Display device

ABSTRACT

In a display device, an image display panel updates an image in a frame cycle including an image scanning period and a vertical blanking period, a light modulation layer is disposed at a back of the panel and switched to a scattering or transmission state depending on an electric field applied, a light source emits light which enters the light modulation layer from its side and travels therethrough, electrodes are formed according to divided areas of the light modulation layer arranged in a direction of the light and apply the electric field to the light modulation layer, and a controller drives the electrodes in synchronization with image scanning to switch the divided areas to the scattering state in order during the image scanning period, and drives the electrodes according to distances from the side to control the scattering state on the individual divided areas during the vertical blanking period.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/154,256, filed on Oct. 8, 2018, which application is a divisional ofSer. No. 15/421,554, filed on Feb. 1, 2017. Application Ser. No.15/421,554 claims the benefit of priority of Japanese Patent ApplicationNo. 2016-038609, filed on Mar. 1, 2016, the contents of which areincorporated by reference.

FIELD

The embodiments discussed herein are related to a display device.

BACKGROUND

With a display device including a backlight, the technique of dividing adisplay surface into a plurality of areas and on-off controlling lightfrom the backlight according to areas is known. With a side light sourcetype backlight a scattering material is mixed into a transparent resinmaterial to form a light guide member. Light from a light sourcedisposed at a side is scattered by the light guide member. With abacklight having this structure, the backlight is divided into areasparallel with a direction in which light from each light source travels,and light sources disposed according to the areas are on-off controlled.Because light from a light source corresponding to another area is notutilized, light emission efficiency decreases.

In recent years backlights including polymer dispersed liquid crystal(PDLC) as a light guide body have been known. With the PDLC, switchingbetween a scattering state in which incident light is scattered and atransmission state in which incident light is transmitted is performedby controlling a voltage applied to area electrodes. With a backlightincluding the PDLC, control is exercised so that the PDLC will be in thescattering state. By doing so, light emitted from a side light source isemitted toward a display surface. For example, area electrodes areformed according to areas formed in a direction intersecting a directionin which light from a light source travels, and switching is performedbetween the scattering state and the transmission state of the PDLC. Bydoing so, backlight light is controlled according to the areas. With adisplay device using PDLC, divided areas are formed in a directionintersecting a direction in which light travels. Therefore, backlightlight is controlled according to the divided areas in a state in which alight source is always on.

See, for example, Japanese Laid-open Patent Publication No. 2014-102295.

However, if areas are formed in a display device in a directionintersecting a direction in which light from a light source travels, thedistance from the light source differs among different areas. Therefore,as the distance between the light source and an area becomes longer, theintensity of light which enters the area decreases. As a result, if anelectrode is driven uniformly in each area, the luminance of an areamore distant from the light source becomes lower. However, if luminancecontrol is exercised with an area whose luminance is lowest asreference, the luminance of an entire backlight decreases.

SUMMARY

According to an aspect, there is provided a display device including animage display panel which updates an image in a frame cycle including animage scanning period and a vertical blanking period; a light modulationlayer disposed at a back of the image display panel and switched to ascattering state in which incident light is scattered or a transmissionstate in which the incident light is transmitted according to anelectric field applied; a light source which emits light that enters thelight modulation layer from a side thereof and travels in the lightmodulation layer; electrodes which are formed according to divided areasof the light modulation layer arranged in a direction in which the lightfrom the light source travels, and which apply the electric field to thelight modulation layer; and a controller which drives the electrodes insynchronization with image scanning and switches in order the dividedareas to be put into the scattering state, during a first periodcorresponding to the image scanning period, and which drives theelectrodes according to distances from the side to control thescattering state according to the divided areas, during a second periodcorresponding to the vertical blanking period.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of the structure of a display deviceaccording to a first embodiment;

FIG. 2 is a perspective view illustrative of the structure of a displaydevice according to a second embodiment;

FIG. 3 is a sectional view illustrative of an example of the structureof a light guide section of the display device according to the secondembodiment;

FIGS. 4A and 4B are views for describing the function of PDLC;

FIG. 5 illustrates an example of the structure of electrodes of thedisplay device according to the second embodiment;

FIG. 6 illustrates partial drive of a backlight in the display deviceaccording to the second embodiment;

FIG. 7 illustrates the luminance distribution of light from a lightsource of the display device according to the second embodiment;

FIG. 8 illustrates an example of the hardware configuration of thedisplay device according to the second embodiment;

FIG. 9 illustrates an example of the structure of the functions of thedisplay device according to the second embodiment;

FIG. 10 illustrates drive timing of each functional component of thedisplay device according to the second embodiment;

FIG. 11 illustrates an example of a drive pattern of the display deviceaccording to the second embodiment;

FIG. 12 illustrates an example of the luminance distribution of abacklight of the display device according to the second embodiment;

FIG. 13 illustrates an example of driving of an electrode in the secondembodiment;

FIG. 14 illustrates another example of a drive pattern of the displaydevice according to the second embodiment;

FIG. 15 illustrates an example of the structure of a display deviceaccording to a third embodiment;

FIG. 16 is a perspective view illustrative of the structure of a displaydevice according to a fourth embodiment;

FIG. 17 is a sectional view illustrative of an example of the structureof a light guide section of the display device according to the fourthembodiment;

FIG. 18 illustrates the luminance distribution of light from lightsources of the display device according to the fourth embodiment;

FIG. 19 illustrates an example of the structure of the functions of thedisplay device according to the fourth embodiment;

FIG. 20 illustrates partial drive of a backlight in the display deviceaccording to the fourth embodiment;

FIG. 21 illustrates a first example of a drive pattern of the displaydevice according to the fourth embodiment;

FIGS. 22A and 22B illustrate the luminance distribution of a backlightin the first example of a drive pattern of the display device accordingto the fourth embodiment;

FIG. 23 illustrates a second example of a drive pattern of the displaydevice according to the fourth embodiment;

FIGS. 24A and 24B illustrate the luminance distribution of the backlightin the second example of a drive pattern of the display device accordingto the fourth embodiment;

FIG. 25 illustrates a third example of a drive pattern of the displaydevice according to the fourth embodiment;

FIGS. 26A and 26B illustrate the luminance distribution of the backlightin the third example of a drive pattern of the display device accordingto the fourth embodiment;

FIG. 27 illustrates an example of a drive pattern of a display deviceaccording to a fifth embodiment;

FIGS. 28A and 28B illustrate the luminance distribution of a backlightin the display device according to the fifth embodiment;

FIG. 29 illustrates an example of a drive pattern of a display deviceaccording to a sixth embodiment;

FIG. 30 illustrates an example of a drive pattern of a display deviceaccording to a seventh embodiment;

FIG. 31 illustrates an example of a drive pattern of a display deviceaccording to an eighth embodiment;

FIGS. 32A and 32B illustrate the luminance distribution of a backlightin the display device according to the eighth embodiment;

FIG. 33 illustrates an example of a drive pattern of a display deviceaccording to a ninth embodiment;

FIG. 34 illustrates an example of a drive pattern of a display deviceaccording to a tenth embodiment;

FIGS. 35A and 35B illustrate the luminance distribution of a backlightin the display device according to the tenth embodiment;

FIG. 36 illustrates an example of a drive pattern of a display deviceaccording to an eleventh embodiment;

FIG. 37 illustrates partial drive of a backlight in a display deviceaccording to a twelfth embodiment;

FIG. 38 illustrates an example of a drive pattern of the display deviceaccording to the twelfth embodiment;

FIG. 39 illustrates the luminance distribution of a backlight in thedisplay device according to the twelfth embodiment;

FIG. 40 illustrates an example of the structure of the functions of adisplay device according to a thirteenth embodiment;

FIG. 41 illustrates drive timing of each functional section of thedisplay device according to the thirteenth embodiment;

FIG. 42 illustrates an example of a display screen of the display deviceaccording to the thirteenth embodiment;

FIG. 43 illustrates an example of a drive pattern of the display deviceaccording to the thirteenth embodiment; and

FIG. 44 illustrates the luminance distribution of a backlight in thedisplay device according to the thirteenth embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments will now be described with reference to the accompanyingdrawings.

Disclosed embodiments are simple examples. It is a matter of course thata proper change which suits the spirit of the invention and which willreadily occur to those skilled in the art falls within the scope of thepresent invention. Furthermore, in order to make description clearer,the width, thickness, shape, or the like of each component mayschematically be illustrated in the drawings compared with the realstate. However, it is a simple example and the interpretation of thepresent invention is not restricted.

In addition, in the present invention and the drawings the samecomponents that have already been described in previous drawings aremarked with the same numerals and detailed descriptions of them may beomitted according to circumstances.

(First Embodiment)

A display device according to a first embodiment will be described bythe use of FIG. 1. FIG. 1 illustrates an example of the structure of adisplay device according to a first embodiment.

A display device 1 according to a first embodiment includes an imagedisplay panel 2, a first electrode 3, a light modulation layer 4, asecond electrode 5, a light source 6, and a controller 7. In FIG. 1,these components are moved with respect to one another. In reality,however, the image display panel 2, the first electrode 3, the lightmodulation layer 4, and the second electrode 5 are stacked in this orderfrom a user. The first electrode 3, the light modulation layer 4, thesecond electrode 5, and the light source 6 function as a backlight ofthe image display panel 2. Furthermore, the display device 1 controlsbacklight light according to divided areas 4 a, 4 b, 4 c, and 4 d of thelight modulation layer 4 arranged in a direction in which light from thelight source 6 travels. Light emitted from the light source 6 enters thelight modulation layer 4, is scattered in the light modulation layer 4,and is emitted to the image display panel 2 side as the backlight light.

The image display panel 2 receives an image signal and updates an imagein a frame cycle. One frame period corresponding to the frame cycleincludes an image scanning period during which an image signal iswritten to the image display panel 2 and a vertical blanking periodduring which an image signal is not written. Image scanning is performedin order on display areas 2 a, 2 b, 2 c, and 2 d right over the areas 4a, 4 b, 4 c, and 4 d, respectively, of the backlight during the imagescanning period. The controller 7 drives the image display panel 2 andmakes the image display panel 2 perform image scanning in the directionfrom the display area 2 a to the display area 2 d or in the directionfrom the display area 2 d to the display area 2 a.

The first electrode 3 and the second electrode 5 are opposite each otherwith the light modulation layer 4 therebetween and apply an electricfield to the light modulation layer 4. The first electrode 3 and thesecond electrode 5 are transparent electrodes and are made of atransparent conductive film such as indium tin oxide (ITO). The firstelectrode 3 includes partial electrodes 3 a, 3 b, 3 c, and 3 d formed inthe areas 4 a, 4 b, 4 c, and 4 d respectively. The partial electrodes 3a, 3 b, 3 c, and 3 d are coupled to the controller 7. Determined drivevoltages are supplied individually to the partial electrodes 3 a, 3 b, 3c, and 3 d. The second electrode 5 is a common electrode and is formedcorresponding to the areas 4 a, 4 b, 4 c, and 4 d or integrally. Acommon potential is supplied to the second electrode 5. An electricfield is generated in the area 4 a, 4 b, 4 c, or 4 d due to thedifference between the drive voltage supplied to the partial electrode 3a, 3 b, 3 c, or 3 d and the common potential supplied to the secondelectrode 5. In FIG. 1, the first electrode 3 is disposed between thelight modulation layer 4 and the image display panel 2. However, thedisposition of the first electrode 3 and the second electrode 5 may bereversed. Furthermore, as long as an electric field is applied to thelight modulation layer 4, both of the first electrode 3 and the secondelectrode 5 may be on one side of the light modulation layer 4.

An electric field is applied to the area 4 a, 4 b, 4 c, or 4 d of thelight modulation layer 4 due to the difference in voltage between thecorresponding partial electrode 3 a, 3 b, 3 c, or 3 d and the secondelectrode 5. The light modulation layer 4 switches to a scattering stateor a transmission state depending on an applied electric field. In thescattering state, the light modulation layer 4 scatters light emittedfrom the light source 6 and emits part of a scattered light toward theimage display panel 2. Furthermore, in the transmission state, the lightmodulation layer 4 transmits light emitted from the light source 6. Atransmitted light travels in a traveling direction to the next area.Viewed from the image display panel 2 side, an area in the scatteringstate is luminous and an area in the transmission state is not luminous.Time during which the light modulation layer 4 is in the scatteringstate is referred to as scattering time. Light modulation layers 4 areof two types: a first type and a second type. A light modulation layer 4of the first type goes into the scattering state at the time of anelectric field being applied and goes into the transmission state at thetime of an electric field not being applied. A light modulation layer 4of the second type goes into the transmission state at the time of anelectric field being applied and goes into the scattering state at thetime of an electric field not being applied. The light modulation layer4 of the first type will now be described. However, description of thelight modulation layer 4 of the first type is also applied to a lightmodulation layer 4 of the second type.

The light source 6 is disposed near a side of the light modulation layer4 and emits light. This light enters the light modulation layer 4 fromthe side and travels in the light modulation layer 4. The light entersthe light modulation layer 4 and travels toward a side opposite the sidefrom which the light enters the light modulation layer 4. Hereinafterthe side from which light from the light source 6 enters the lightmodulation layer 4 will be referred to as an incident surface. As thedistance from the incident surface increases, light which travels inthis way in the light modulation layer 4 is attenuated and its intensityis reduced. In the example of FIG. 1, the intensity of light whichenters each area of the light modulation layer 4 is reduced as area 4d>area 4 c>area 4 b>area 4 a. The light source 6 is coupled to thecontroller 7 and the controller 7 exercises on-off-control of lightemission and controls the amount of light at light emission time.

The controller 7 controls driving of the partial electrodes 3 a, 3 b, 3c, and 3 d and the luminance of the light source 6 in synchronizationwith a frame cycle of the image display panel 2. The controller 7 is,for example, a processor such as a central processing unit (CPU).However, the controller 7 may include a special-purpose electroniccircuit such as an application specific integrated circuit (ASIC) or afield programmable gate array (FPGA).

The controller 7 exercises control in synchronization with the framecycle of the image display panel 2 so as to apply determined voltages inorder between the partial electrodes 3 a, 3 b, 3 c, and 3 d andcorresponding portions of the second electrode 5 and switch the areas 4a, 4 b, 4 c, and 4 d to the scattering state in order. Hereinafter thisprocess of switching the areas 4 a, 4 b, 4 c, and 4 d to the scatteringstate in order will be referred to as backlight scanning. The controller7 performs backlight scanning with a period corresponding to an imagescanning period and a period corresponding to a vertical blanking periodas a first period and a second period respectively. An image scanningdirection and a backlight scanning direction are the same.

During the first period the controller 7 performs backlight scanning onthe areas 4 a, 4 b, 4 c, and 4 d on which image scanning has ended insynchronization with the image scanning. For example, the controller 7switches in order the areas 4 a, 4 b, 4 c, and 4 d to be put into thescattering state to timing at which the image display panel 2 switchesthe display areas 2 a, 2 b, 2 c, and 2 d on which it performs imagescanning. For example, for a period for which image scanning on thedisplay area 2 a has ended and image scanning is performed on thedisplay area 2 b, the controller 7 switches the area 4 a correspondingto the display area 2 a to the scattering state. The controller 7applies a determined voltage to the corresponding partial electrode 3 ato apply an electric field to the area 4 a. The controller 7 then putsthe area 4 b into the scattering state for a period for which imagescanning is performed on the display area 2 c. In this way thecontroller 7 switches in order an area on which image scanning has endedto the scattering state in synchronization with image scanning on thedisplay area 2 a, 2 b, 2 c, or 2 d. An area other than the area put intothe scattering state is put into the transmission state. As statedabove, during the first period, scattering time of the area 4 a,scattering time of the area 4 b, scattering time of the area 4 c, andscattering time of the area 4 d are equal and are equal to imagescanning time.

During the second period, the controller 7 controls the scattering stateof the area 4 a, 4 b, 4 c, or 4 d according to the distance between thearea 4 a, 4 b, 4 c, or 4 d and the incident surface and performsbacklight scanning. For example, the controller 7 makes scattering timeof the area 4 a distant from the incident surface the longest. As thedistance from the incident surface decreases, the controller 7 makesscattering time shorter.

An example of the operation of the display device 1 having the abovestructure will be described.

During the image scanning period the image display panel 2 performsimage scanning on the display areas 2 a, 2 b, 2 c, and 2 d in thatorder. The order of image scanning may be reversed. The controller 7switches the area 4 a, 4 b, 4 c, or 4 d to the scattering state insynchronization with image scanning in the order in which the imagescanning has ended. For example, the controller 7 exercises control sothat image scanning performed on the display area 2 a, 2 b, 2 c, or 2 dwill precede backlight scanning performed on the area 4 a, 4 b, 4 c, or4 d by one area. For example, the controller 7 exercises control so asto put the area 4 a corresponding to the display area 2 a on which imagescanning has ended into the scattering state for a period for whichimage scanning is performed on the display area 2 b. At this time thecontroller 7 exercises control so as to put the other areas 4 b, 4 c,and 4 d into the transmission state. In this way, image scanningsynchronizes with backlight scanning with one area shifted. The amountof a delay between image scanning and backlight scanning is not limitedto one area. Backlight scanning may properly be delayed by an integralmultiple of an image scanning period of one area.

As has been described, the display device 1 switches in order areascorresponding to display areas on which image scanning has ended to thescattering state in synchronization with image scanning. As a result,before the display device 1 switches an area to the scattering state,the display device 1 finds required luminance for an image in a displayarea. This makes it possible to perform a local dimming processaccording to areas without using a frame memory. The local dimmingprocess is a process in which the luminance of the backlight iscontrolled to a displayed image on the basis of an image signal of adisplay area. Hereinafter it is assumed that the luminance of thebacklight is luminance obtained during a determined period (one frameperiod, for example). For example, the luminance of the backlight is avalue based on time in a frame period for which an area is in thescattering state and the intensity of light which enters the area in thescattering state.

The image display panel 2 does not perform image scanning during thevertical blanking period. During the second period the controller 7distributes scattering time according to the distance between the area 4a, 4 b, 4 c, or 4 d and the incident surface. As light from the lightsource 6 travels further in the light modulation layer 4, it attenuates.Scattering time of the area 4 a, scattering time of the area 4 b,scattering time of the area 4 c, and scattering time of the area 4 d areequal during the first period. Accordingly, as the distance between anarea and the incident surface increases, the intensity of backlightlight emitted decreases. The controller 7 determines scattering time ofeach area on the basis of the amount of a decrease in luminancecorresponding to the distance from the incident surface. The controller7 makes scattering time of the area 4 a most distant from the incidentsurface the longest and makes scattering time shorter in the order ofthe areas 4 b, 4 c, and 4 d.

In this way, the display device 1 increases the luminance of thebacklight in the second period. The display device 1 distributesscattering time in the second period to the areas 4 a, 4 b, 4 c, and 4 don the basis of a decrease in luminance corresponding to the distancefrom the light source 6. For example, in order to realize the samebacklight light as obtained when the area 4 d nearest the light source 6becomes luminous in the first period, the display device 1 distributesscattering time during the second period to the other areas 4 a, 4 b,and 4 c. By doing so, the luminance of the areas 4 a, 4 b, 4 c, and 4 dare uniformized regardless of the distance from the light source 6.Furthermore, because the light modulation layer 4 is put into thescattering state for a period for which image scanning is not performed,the luminance of the whole of the areas 4 a, 4 b, 4 c, and 4 d isincreased.

(Second Embodiment)

Next, a display device according to a second embodiment will bedescribed. FIG. 2 is a perspective view illustrative of the structure ofa display device according to a second embodiment.

With a display device 100 according to a second embodiment a light guidesection 130 is disposed at a back of a liquid crystal display (LCD)panel 120. Furthermore, a light source 140 is disposed along a side ofthe light guide section 130 and emits light toward the light guidesection 130. The light guide section 130 and the light source 140 makeup a backlight. For convenience, it is assumed in the followingdescription that a direction in which the light source 140 is disposedis an X direction, that a direction in which light from the light source140 travels is a Y direction, and that a direction in which the lightguide section 130 and the LCD panel 120 are stacked is a Z direction.

The LCD panel 120 performs display by the use of light emitted from thelight guide section 130.

The light guide section 130 has an emission surface opposite a displaysurface of the LCD panel 120. The light guide section 130 scatters lightemitted from the light source 140 and emits light from the emissionsurface. The luminance of the backlight is determined by the amount oflight emitted from the emission surface in a determined period. With thedisplay device 100 the luminance of the backlight is controlledaccording to areas obtained by dividing the emission surface of thelight guide section 130 in the Y direction. Hereinafter the areas arereferred to as an area CH1, an area CH2, an area CH3, an area CH4, anarea CH5, an area CH6, an area CH7, an area CH8, an area CH9, and anarea CH10 in descending order of distance from the light source 140. Ifthere is no need to designate a specific area for description,hereinafter the term “area” will simply be used. Furthermore, the lightguide section 130 performs a local dimming process. That is to say, thelight guide section 130 analyzes a displayed image on the LCD panel 120for each area and controls the luminance of the backlight to an image ineach area.

Next, each component will be described in order.

FIG. 3 is a sectional view illustrative of an example of the structureof a light guide section of the display device according to the secondembodiment. FIG. 3 is a sectional view taken along the line A-A′ of FIG.2. CH10, CH9, CH8, and CH7 indicate areas.

A PDLC layer 133, an upper electrode 134, a lower electrode 135, andorientation films 136 and 137 are stacked between transparent substrates131 and 132 of the light guide section 130. In the example of FIG. 3,the transparent substrate 132, the lower electrode 135, the orientationfilm 137, the PDLC layer 133, the orientation film 136, the upperelectrode 134, and the transparent substrate 131 are stacked indescending order of distance from the LCD panel 120. Furthermore, areflection sheet 138 is disposed on a side of the transparent substrate132 opposite to the LCD panel 120.

The transparent substrates 131 and 132 support the PDLC layer 133, theupper electrode 134, the lower electrode 135, and the orientation films136 and 137. Each of the transparent substrates 131 and 132 is asubstrate, such as a glass plate or a plastic film, which is transparentto a visible light. A surface of the transparent substrate 131 oppositethe LCD panel 120 is an emission surface 139 which emits light scatteredin the PDLC layer 133.

PDLC 1331 is formed in an area in the PDLC layer 133 partitioned withspacers 1332. The PDLC layer 133 is an example of the light modulationlayer 4 in the first embodiment. With the display device 100 the PDLC1331 switches to the scattering state at the time of applying anelectric field and switches to the transmission state at the time of notapplying an electric field. The spacer 1332 is disposed between PDLC1331 and PDLC 1331. Furthermore, the spacer 1332 maintains the distancebetween the transparent substrates 131 and 132. The spacer 1332 isformed by the use of a transparent material and transmits light whichenters in the Y direction. The spacer 1332 is preferably formed by theuse of a material whose light transmittance is higher than that of thePDLC 1331 in the transmission state. An increase in the lighttransmittance of the spacer 1332 reduces attenuation of light travelingin the PDLC layer 133. The spacer 1332 may not be formed. In this case,PDLC 1331 is disposed in an area of the spacer 1332.

The upper electrode 134 and the lower electrode 135 are disposed inareas opposite each other with the PDLC 1331 therebetween. The upperelectrode 134 and the lower electrode 135 are transparent conductivefilms. With the display device 100, the upper electrode 134 is an areaelectrode and the lower electrode 135 is a common electrode. An electricfield is applied to the PDLC 1331 on the basis of the difference inpotential between the upper electrode 134 and the lower electrode 135.

Each of the orientation films 136 and 137 orients liquid crystalmolecules in the PDLC 1331 in a determined direction at the time of anelectric field not being applied. An orientation film is a verticalorientation film, a horizontal orientation film, or the like.

A reflection sheet 138 has the functions of reflection, diffusion,scattering, and the like. The reflection sheet 138 returns to the PDLClayer 133 light which leaks out from the transparent substrate 132disposed on a side opposite to the emission surface 139. This increaseslight emitted from the emission surface 139 and increases luminance.Furthermore, because the reflection sheet 138 suppresses light leakageto the outside, light emitted from the light source 140 is efficientlyutilized. Foamed polyethylene terephthalate (PET), a silver-evaporatedfilm, a multilayer reflection film, white PET, or the like is used asthe reflection sheet 138.

FIGS. 4A and 4B are views for describing the function of PDLC. FIGS. 4Aand 4B are enlarged views of the PDLC 1331 portion of FIG. 3. The upperelectrode 134, the lower electrode 135, the orientation film 136, or theorientation film 137 is not illustrated in FIGS. 4A and 4B. FIG. 4Aillustrates the transmission state and FIG. 4B illustrates thescattering state.

The PDLC 1331 will now be described. The PDLC 1331 contains a liquidcrystalline monomer 1331 a and liquid crystal molecules 1331 b dispersedin the liquid crystalline monomer 1331 a. The liquid crystalline monomer1331 a and the liquid crystal molecules 1331 b are equal in refractiveindex anisotropy and differ in responsiveness to an electric field. Tobe more specific, the liquid crystalline monomer 1331 a and the liquidcrystal molecules 1331 b are equal in ordinary refractive index andextraordinary refractive index. For example, refractive index deviationcaused by manufacturing errors or the like is allowable. On the otherhand, the responsiveness of the liquid crystal molecules 1331 b to anelectric field is higher than the responsiveness of the liquidcrystalline monomer 1331 a to an electric field. For example, the liquidcrystalline monomer 1331 a has a striped structure or a porous structurewhich does not respond to an electric field or has a rod-shapedstructure whose speed of a response to an electric field is slower thanthe speed of a response of the liquid crystal molecules 1331 b to anelectric field. Furthermore, for example, the liquid crystalline monomer1331 a is orientable and is oriented in the orientation direction of theliquid crystal molecules 1331 b or the orientation direction of theorientation films 136 and 137. It is desirable that the liquidcrystalline monomer 1331 a be a monomer polymerized by hardening bylight or heat. If a polymer is produced by polymerizing the liquidcrystalline monomer 1331 a, it is desirable that the liquid crystalmolecules 1331 b and a liquid crystalline polymer (high molecularmaterial) be hardened in a state in which the liquid crystal molecules1331 b and the liquid crystalline polymer remain equal in ordinaryrefractive index and extraordinary refractive index. Furthermore, it isdesirable that the responsiveness of the liquid crystal molecules 1331 bto an electric field be higher than the responsiveness of the liquidcrystalline polymer to an electric field. Hereinafter description of aliquid crystalline monomer also applies to a liquid crystalline polymerproduced by polymerizing the liquid crystalline monomer.

When there is no difference in potential between the upper electrode 134and the lower electrode 135 and an electric field is not applied, theabove PDLC 1331 is in the transmission state illustrated in FIG. 4A.That is to say, in a state in which an electric field is not applied,the liquid crystalline monomer 1331 a and the liquid crystal molecules1331 b which are equal in refractive index anisotropy are oriented inthe same direction by the functions of the orientation films 136 and137. Therefore, there is almost no difference in refractive index in alldirections between the liquid crystalline monomer 1331 a and the liquidcrystal molecules 1331 b. Light L1, L2, and L3 which enters the PDLC1331 from a side in this state is not scattered at the boundariesbetween the liquid crystalline monomer 1331 a and the liquid crystalmolecules 1331 b. The light L1, L2, and L3 travels in the Y directionand passes through the PDLC 1331. In FIG. 4A, directions in which thelight L1, L2, and L3 travels are indicated by dotted arrows.

On the other hand, when an electric field is applied due to thedifference in potential between the upper electrode 134 and the lowerelectrode 135, the PDLC 1331 is in the scattering state illustrated inFIG. 4B. That is to say, in a state in which an electric field isapplied, the orientation direction of the liquid crystal molecules 1331b whose responsiveness to the electric field is high changes. However,the orientation direction of the liquid crystalline monomer 1331 a doesnot change. As a result, there is a great difference in refractive indexin all directions between the liquid crystalline monomer 1331 a and theliquid crystal molecules 1331 b. Light L1, L2, and L3 which enters thePDLC 1331 from the side in this state is scattered at the boundariesbetween the liquid crystalline monomer 1331 a and the liquid crystalmolecules 1331 b. In FIG. 4B, directions in which the light L1, L2, andL3 travels are indicated by dotted arrows and scattered light isindicated by L11, L21, and L31.

As has been described, when an electric field is not applied, the PDLC1331 is in the transmission state. When an electric field is applied dueto the difference in potential between the upper electrode 134 and thelower electrode 135, the PDLC 1331 is in the scattering state. If thePDLC 1331 is PDLC of the above second type, then the relationshipbetween the scattering state and the transmission state and applicationof an electric field based on the difference in potential between theupper electrode 134 and the lower electrode 135 is inverted.

FIG. 5 illustrates an example of the structure of electrodes of thedisplay device according to the second embodiment. CH1 through CH10indicate areas in which partial electrodes are arranged.

The upper electrode 134 is formed by performing patterning ofslit-shaped ITO electrodes for each areas. With the upper electrode 134,individual signal lines are connected to artial electrodes formed foreach areas to supply different drive signals. For example, Vch1 issupplied to a partial electrode in the area CH1. Similarly, Vch10 issupplied to a partial electrode in the area CH10. The same applies tothe areas CH2 through CH9.

The lower electrode 135 is formed by patterning slit-shaped ITOelectrodes for each area. A partial electrode of the lower electrode 135formed in an area is opposite a partial electrode of the upper electrode134 formed in the same area. With the lower electrode 135, a commonsignal line is connected to partial electrodes formed in each area tosupply a voltage Vcom. The upper electrode 134 and the lower electrode135 are driven by producing a potential difference between a partialelectrode of the upper electrode 134 and a partial electrode of thelower electrode 135 formed in each area. Hereinafter a combination of apartial electrode of the upper electrode 134 and a partial electrode ofthe lower electrode 135 disposed opposite each other in each area willbe referred to as area electrodes.

In each area, the PDLC 1331 is arranged in a portion in which an areaelectrode illustrated in FIG. 5 is formed and the spacer 1332 isarranged in a portion in which an area electrode illustrated in FIG. 5is not formed. Furthermore, the shape of each of the upper electrode 134and the lower electrode 135 is not limited to that illustrated in FIG.5. As long as a desired electric field is generated in each area, eachof the upper electrode 134 and the lower electrode 135 may have anyshape.

Partial drive of the backlight in the above display device 100 will bedescribed. FIG. 6 illustrates partial drive of the backlight in thedisplay device according to the second embodiment.

Light L4 is emitted from the light source 140 and enters the PDLC layer133. If the light L4 is not scattered in the PDLC layer 133, the lightL4 travels in the Y direction while being totally reflected by thetransparent substrates 131 and 132. The spacer 1332 transmits incidentlight. Accordingly, the light L4 travels straight in the spacer 1332.

A case where the area CH8 is driven will now be described. A drivevoltage is applied to area electrodes corresponding to the area CH8 togenerate an electric field in the area CH8. As a result, the PDLC 1331in the area CH8 goes into the scattering state. At this time a drivevoltage is not applied to area electrodes corresponding to the areaCH10, the area CH9, or the area CH7. Accordingly, an electric field isnot generated in the area CH10, the area CH9, or the area CH7 and thePDLC 1331 in the area CH10, the area CH9, and the area CH7 go into thetransmission state. That is to say, the PDLC layer 133 in the area CH10,the area CH9, the area CH8, and the area CH7 go into the transmissionstate, the transmission state, the scattering state, and thetransmission state, respectively.

Because the area CH10 which the light L4 first enters is in thetransmission state, the light L4 travels straight. The light L4 passesthrough the area CH10 and enters the area CH9. Because the area CH9 isalso in the transmission state, the light L4 travels straight. The lightL4 passes through the area CH9 and enters the area CH8. Because the areaCH8 is in the scattering state, the light L4 is scattered. Of ascattered light, light which travels to the emission surface 139 isemitted from the emission surface 139. Light which travels to thetransparent substrate 132 is returned into the PDLC 1331 by thereflection sheet 138. The light returned into the PDLC 1331 in the areaCH8 is scattered again. Furthermore, because most of the light L4 isscattered in the area CH8, the light L4 does not enter the next areaCH7. It is visually recognized from the LCD panel 120 side that in thelight guide section 130 in this state, the area CH8 is luminous and thatthe other areas CH10, CH9, and CH7 are not luminous.

In this way, the display device 100 is able to perform partial drive ofthe backlight by putting areas into the scattering state in order.Unless otherwise stated, hereinafter it is assumed that when an area isput into the scattering state, control is exercised so as to put theother areas into the transmission state.

FIG. 7 illustrates the luminance distribution of light from the lightsource of the display device according to the second embodiment. FIG. 7is a plan view of the light guide section 130 and the light source 140from the Z direction and a graph indicative of the luminance of eacharea. A dotted line on the graph indicates the boundary between areas.

The light source 140 is a linear light source and emits light which isuniform in the X direction toward the light guide section 130. Forexample, the light source 140 is formed by arranging light emittingdiodes (LEDs) in a row in the X direction. The intensity of lightemitted from the light source 140 is controlled by controlling a drivecurrent. In the following description a drive current for driving thelight source 140 is common to the whole of the light source 140. Forexample, however, a plurality of LEDs arranged may individually becontrolled.

As described by the use of FIG. 6, light from the light source 140enters the display device 100 from the side of the light guide section130 and travels in the PDLC layer 133 in the Y direction. The lighttraveling in the PDLC layer 133 in the Y direction is attenuated by thePDLC layer 133. As a result, as the distance from the light source 140increases, its luminance decreases.

The intensity of light which enters the area CH10 nearest the side ofthe light guide section 130 is highest. As the distance from the lightsource 140 increases, the luminance of the incident light decreases. Theintensity of the light which enters the area CH1 is lowest. That is tosay, the intensity of light which enters each area is as follows:CH10>CH9>CH8>CH7>CH6>CH5>CH4>CH3>CH2>CH1.

FIG. 8 illustrates an example of the hardware configuration of thedisplay device according to the second embodiment.

The whole of the display device 100 is controlled by a control unit 110.

The control unit 110 includes a CPU 111, a random access memory (RAM)112, and a read only memory (ROM) 113. A plurality of peripheral unitsare coupled to the control unit 110 via a bus 119 so as to input oroutput a signal.

The CPU 111 controls the whole of the display device 100 on the basis ofan operating system (OS) program and application programs stored in theROM 113 and various pieces of data expanded in the RAM 112. When the CPU111 performs a process, the CPU 111 may operate on the basis of the OSprogram and an application program temporarily stored in the RAM 112.

The RAM 112 is used as main storage of the control unit 110. The RAM 112temporarily stores at least part of the OS program or an applicationprogram executed by the CPU 111. In addition, the RAM 112 stores variouspieces of data which the CPU 111 needs to perform a process.

The ROM 113 is a read only semiconductor memory and stores the OSprogram, the application programs, and fixed data which is notrewritten. Furthermore, a semiconductor memory, such as a flash memory,may be used as auxiliary storage in place of the ROM 113 or in additionto the ROM 113.

The plurality of peripheral units connected to the bus 119 are a displaydriver 114, a light source driver 115, a PDLC driver 116, aninput-output interface 117, and a communication interface 118.

A LCD panel 120 is coupled to the display driver 114. The display driver114 outputs an image signal to the LCD panel 120 to display an image.

The light source 140 is coupled to the light source driver 115. Thelight source driver 115 drives the light source 140 and controls theintensity of light which enters the PDLC layer 133.

The light guide section 130 is coupled to the PDLC driver 116. The PDLCdriver 116 applies an electric field to the PDLC layer 133 by applying adrive voltage to area electrodes formed in the light guide section 130.

An input device used for inputting a user's instructions is coupled tothe input-output interface 117. An input device, such as a keyboard, amouse used as a pointing device, or a touch panel, is coupled. Theinput-output interface 117 transmits to the CPU 111 a signal transmittedfrom the input device.

The communication interface 118 is connected to a network 190. Thecommunication interface 118 transmits data to or receives data fromanother computer or a communication apparatus via the network 190.

By adopting the above hardware configuration, the processing functionsin the second embodiment are realized.

FIG. 9 illustrates an example of the structure of the functions of thedisplay device according to the second embodiment.

With the display device 100 a signal processing section 150 receives animage signal and generates signals on the basis of the image signal fordriving the display driver 114, the light source driver 115, and thePDLC driver 116. The signal processing section 150 includes an imageprocessing block 151, a timing generation block 152, an image analysisblock 153, a light source data storage block 154, and a drive patterndetermination block 155. The image processing block 151, the timinggeneration block 152, the image analysis block 153, and the drivepattern determination block 155 are realized by, for example, aprocessor such as the CPU 111. The light source data storage block 154is realized by a storage area secured in the RAM 112, the ROM 113, orthe like.

The image processing block 151 receives an image signal, converts theimage signal to a display signal, and outputs the display signal to thedisplay driver 114. The image signal includes color informationcorresponding to each pixel of the LCD panel 120. Pixels are arranged ina matrix in the LCD panel 120. Each pixel is made up of three subpixels.For example, each pixel is made up of a red subpixel, a green subpixel,and a blue subpixel. A pixel made up of a red subpixel, a greensubpixel, and a blue subpixel is an example. For example, a pixel may bemade up of four subpixels, that is to say, a red subpixel, a greensubpixel, a blue subpixel, and a white subpixel. Furthermore, a pixelmay be made up of other subpixels, such as a cyan subpixel, a magentasubpixel, and a yellow subpixel. The image signal includes colorinformation on, for example, red, green, and blue. If a pixel is made upof four subpixels, that is to say, a red subpixel, a green subpixel, ablue subpixel, and a white subpixel, then the image processing block 151converts the image signal including, for example, red, green, and blueto a display signal including red, green, blue, and white and outputsthe display signal to the display driver 114.

The timing generation block 152 outputs a timing signal to the displaydriver 114 and the PDLC driver 116. For example, the timing generationblock 152 outputs a vertical synchronizing signal and a horizontalsynchronizing signal used for scanning. The timing generation block 152generates a timing signal by, for example, counting a clock signal. Thedisplay driver 114 performs image scanning to the timing signal by theuse of the display signal acquired from the image processing block 151.The PDLC driver 116 applies a drive voltage to area electrodes to thetiming signal. As a result, control is exercised so as to put the PDLC1331 corresponding to the area electrodes to which the drive voltage isapplied into the scattering state.

The image analysis block 153 receives the image signal and calculatesrequired luminance values for each area. For example, a requiredluminance value is the luminance of the backlight required for displayin an area on the basis of the image signal. When local dimming isperformed, a required luminance value is an index of the intensity ofbacklight light emitted from each area of the PDLC layer 133. In orderto control the luminance of the backlight, the display signal of theimage processing block 151 may be corrected to the luminance of thebacklight.

The light source data storage block 154 stores luminance distributiontables in which the luminance of the backlight is recorded forrespective areas. The luminance distribution tables indicate therelationship between the areas indicated in the graph of FIG. 7 and theluminance of the backlight. For example, the light source 140 is drivenby a determined drive current and the areas are driven under the sameconditions. The intensity of light emitted at that time from the lightguide section 130 is measured and is used as a luminance value of thebacklight. A luminance value of the backlight corresponds to theluminance of incident light. A luminance value of the backlight isassociated with an identification number of an area and is registered ina luminance distribution table. A luminance distribution table isprepared by measuring a luminance value of the backlight in advance.

The drive pattern determination block 155 determines a drive pattern ofan area on the basis of a required luminance value acquired from theimage analysis block 153 and a luminance distribution table. Theluminance of the backlight obtained at the time of driving the area at adetermined voltage for a determined time is found from the luminancedistribution table. For example, the drive pattern determination block155 calculates the luminance of the backlight obtained during scatteringtime in a main lighting period assigned to the area. When the luminanceof the backlight calculated is lower than the required luminance value,the drive pattern determination block 155 calculates scattering timeneeded for the area in order to obtain a luminance value correspondingto a deficiency. A luminance increase period is assigned to the areawhich is short of luminance. A drive pattern is determined so that eacharea will satisfy a required luminance value. Furthermore, for example,the following method may be adopted. A drive pattern in which a requiredluminance value is largest in each area is formed in advance and iscorrected on the basis of a required luminance value. For example, adrive pattern includes the magnitude of a drive current used for drivingthe light source 140 and setting of scattering time during which thePDLC driver 116 applies a drive voltage to corresponding areaelectrodes.

Drive timing of each component of the display device 100 having theabove structure will be described.

FIG. 10 illustrates drive timing of each functional component of thedisplay device according to the second embodiment. FIG. 10 illustratestiming of a vertical synchronizing signal Vsync, a horizontalsynchronizing signal Hsync, an image signal DE, image scanning by thedisplay driver 114, and backlight scanning by the PDLC driver 116 duringone frame period.

Image scanning and backlight scanning of the display device 100 areperformed at timing generated by the vertical synchronizing signalVsync. A fall to the next fall of the vertical synchronizing signalVsync corresponds to one frame. The horizontal synchronizing signalHsync generates timing at which one line of the LCD panel 120 isswitched.

The signal processing section 150 begins to receive an image signal DEat timing based on the vertical synchronizing signal Vsync. The imagesignal DE inputted to the signal processing section 150 is processed andis transmitted to the display driver 114. The display driver 114performs image scanning by repeating the process of writing a signalcorresponding to one line to the LCD panel 120 in synchronization withthe horizontal synchronizing signal Hsync. The display driver 114performs image scanning in order from the area CH1 to the area CH10.

The image analysis block 153 acquires the image signal DE inputted inorder and calculates a required luminance value at the time when itacquires a signal corresponding to one area. The drive patterndetermination block 155 determines a drive pattern on the basis of therequired luminance value. A process from acquiring the image signal DEcorresponding to an area to determining a drive pattern is performedduring a period during which the display driver 114 performs imagescanning on the area. The drive pattern determination block 155 controlsthe PDLC driver 116 and the light source driver 115 by the use of thedetermined drive pattern.

In a period during which the display driver 114 performs image scanningon an area next to an area on which image scanning has ended, the PDLCdriver 116 applies a drive voltage to area electrodes in the area onwhich image scanning has ended in synchronization with the horizontalsynchronizing signal Hsync to put the area on which image scanning hasended into the scattering state.

In the example of FIG. 10, the light modulation layer in the area CH1 isin the scattering state (backlight scanning is performed on the areaCH1) during a period during which image scanning on the area CH1 hasended and image scanning is performed on the area CH2. After that,backlight scanning is performed in order on the area CH2 to the areaCH10 in synchronization with image scanning.

In this way, with the display device 100, in a period in which thedisplay driver 114 performs image scanning on an area, a drive patternbased on an image signal corresponding to the area is determined. As aresult, the luminance of the backlight is controlled to the image signalDE. In this case, a frame memory which temporarily stores the imagesignal DE for analyzing the image signal DE is not used.

Hereinafter a period of backlight scanning performed in synchronizationwith the above image scanning will be referred to as a main lightingperiod. Because backlight scanning is performed in synchronization withimage scanning during the main lighting period, scattering time duringwhich each area is put into the scattering state is the same. Asillustrated in FIG. 7, as the distance between an area and the lightsource 140 increases, the intensity of light which enters the areadecreases. Therefore, if the light source 140 and the PDLC layer 133 aredriven under the same conditions, the luminance of the backlight in anarea during the main lighting period decreases. This is the same withthe intensity of incident light illustrated in FIG. 7. With the displaydevice 100, a period corresponding to a vertical blanking period is aluminance increase period and the luminance of an area is increased.

The drive pattern determination block 155 determines a drive pattern sothat the luminance of the backlight during a frame period will become adesired required luminance value for each area by backlight scanningduring the main lighting period and the luminance increase period.

A drive pattern at the time of required luminance values for all areasbeing the same will now be described as an example. The drive patterndetermination block 155 determines a drive pattern so that the luminanceof all areas will be uniform.

FIG. 11 illustrates an example of a drive pattern of the display deviceaccording to the second embodiment. In FIG. 11, a column in the verticaldirection indicates the areas CH1 through CH10 and a row in thehorizontal direction indicates time elapsed. Each time zonecorresponding to the column indicative of the areas CH1 through CH10 inwhich nothing is stated is a period during which a corresponding area isin the transmission state. Furthermore, each time zone indicated byoblique lines is a period during which a corresponding area iscontrolled so as to be in the scattering state. A light source currentis a drive current supplied to the light source 140. Furthermore, athick dotted line indicates image scanning.

In the example of FIG. 11, a constant light source current is suppliedto the light source 140. Because a light source current is constant, theintensity of light emitted from the light source 140 is constant.

The display driver 114 performs image scanning from the area CH1 distantfrom the light source 140 to the area CH10 during an image scanningperiod. The display driver 114 performs image scanning on each area oneline at a time. The scanning period is taken to end scanning of alllines is the same among all areas CH1 through CH10. Furthermore, animage is not written during a vertical blanking period.

The PDLC driver 116 scans the area CH1 through the area CH10 during abacklight scanning period which is equal to one frame period. Backlightscanning is performed in order from the area CH1 to the area CH10 in thesame direction as image scanning on the basis of a timing signal. Atthis time backlight scanning on an area is begun after image scanning onthe area ends. A target area of backlight scanning is switched to thescattering state. On the other hand, the other areas are put into thetransmission state. As a result, only the target area emits backlightlight.

In the example of FIG. 11, after the display driver 114 ends imagescanning on the area CH1, the PDLC driver 116 switches the area CH1 tothe scattering state during the scanning period ts of the next area CH2.Control is exercised during this scanning period ts so that the otherareas will be in the transmission state. Next, the PDLC driver 116exercises control so that the area CH2 will be in the scattering stateduring the scanning period ts during which the display driver 114performs image scanning on the area CH3. This process is repeated to puteach of the areas CH1 through CH10 into the scattering state in orderduring the scanning period ts. By doing so, a main lighting period ends.

The drive pattern determination block 155 determines a drive pattern toincrease the luminance of each area during a luminance increase period.In the example of FIG. 11, a drive pattern for making the luminance ofall the areas uniform is determined with luminance obtained by puttingthe area CH10 nearest the light source 140 into the scattering stateduring the scanning period ts as reference. For example, the drivepattern determination block 155 calculates the luminance of each areaobtained in the main lighting period on the basis of a luminancedistribution table. The drive pattern determination block 155 thencalculates scattering time of each area in the luminance increase periodon the basis of the difference between the calculated luminance of eacharea and the reference luminance. With the drive pattern illustrated inFIG. 11, scattering time tbl of the area CH1 most distant from the lightsource 140 is the longest. In the order of the areas CH1 through CH9,scattering time is reduced as follows: scattering time tb1>tb2>tb3> . .. >tb9. The PDLC driver 116 exercises control on the basis of the drivepattern so as to put the areas CH1 through CH10 into the scatteringstate in order. By doing so, luminance is increased. In the example ofFIG. 11, the value of a light source current in the luminance increaseperiod is equal to the value of a light source current in the mainlighting period. However, a light source current value is set properly.For example, in order to increase luminance, a light source currentvalue in the luminance increase period may be made larger than a lightsource current value in the main lighting period. If the luminance ofthe areas CH9 through CH1 increased exceeds the luminance of a backlightlight in the area CH10 in the main lighting period at this time, thenscattering time is set for the area CH10 to increase luminance.

By exercising the above drive control, the luminance of the backlight inall the areas is uniformized. Furthermore, if scattering time is set toimage scanning in the main lighting period and a luminance increaseperiod is not set in the vertical blanking period, then control isexercised so as to set the luminance of the backlight to luminance inthe lowest area. By doing so, luminance is uniformized. In this way,overall, a higher luminance is obtained by setting the luminanceincrease period.

FIG. 12 illustrates an example of the luminance distribution of thebacklight of the display device according to the second embodiment. InFIG. 12, a vertical axis indicates the luminance of the backlight and ahorizontal axis indicates distance from the light source 140. CH1through CH10 indicate areas.

A thick dotted line in FIG. 12 indicates light source luminancedistribution obtained at the time of driving the areas CH1 through CH10.In this case, the luminance of the light source 140 is the same andconditions under which area electrodes are driven are the same. Asdistance from the light source 140 increases, luminance decreases. Asindicated in FIG. 12, a drive pattern which corrects the amount of adecrease in luminance corresponding to distance from the light source140 is calculated and the areas CH1 through CH10 are driven. By doingso, the luminance of an area distant from the light source 140 isincreased and backlight luminance distribution indicated by a solid lineis obtained.

As has been described, the areas are put into the scattering state inorder during scattering time corresponding to the distance from thelight source 140 in the luminance increase period. By doing so, theluminance of the backlight is uniformized. Furthermore, luminance isincreased not only in the main lighting period but also in the luminanceincrease period. Therefore, the luminance of the entire backlight isincreased.

In addition, after image scanning ends, the PDLC 1331 is put into thescattering state. This makes it possible to perform a local dimmingprocess without using a frame memory. That is to say, while imagescanning is being performed, the image analysis block 153 finds arequired luminance value on the basis of an image signal inputted to theimage analysis block 153 and the image processing block 151 at the sametime. The drive pattern determination block 155 determines a drivepattern on the basis of the required luminance value and gives the PDLCdriver 116 instructions.

Driving of area electrodes which brings about the scattering state of anarea will now be described. FIG. 13 illustrates an example of driving ofan electrode in the second embodiment. In FIG. 13, a vertical axisindicates a voltage value applied to each terminal illustrated in FIG. 5and a horizontal axis indicates time elapsed. Furthermore, dotted lineswhich divide a main lighting period indicate drive periods assigned toareas.

In FIG. 13, for example, each backlight scanning period is one frame.

A voltage of −V (V) or a voltage of +V (V) is inverted every frame andis supplied to a lower electrode 135 of area electrodes as a voltageVcom. A voltage of 2×V (V) is applied to the PDLC 1331 corresponding tothe areas CH1 through CH10 during a period during which a voltage whosepolarity is reverse to that of Vcom is applied. At this time the PDLC1331 goes into the scattering state. On the other hand, when a voltagewhose polarity is the same as that of Vcom is applied, a voltage appliedto the PDLC 1331 is 0 (V). At this time the PDLC 1331 goes into thetransmission state.

As illustrated in FIG. 13, with the display device 100 a voltage whosepolarity is reverse to that of Vcom is applied in order to an upperelectrode 134 of area electrodes in synchronization with image scanningduring a main lighting period. To apply a voltage so as to create avoltage difference between an upper electrode 134 and a lower electrode135 of area electrodes will be referred to as “apply a drive voltage”.

In the example of FIG. 13, a luminance increase period is distributed inthe following way. Scattering time of the area most distant from thelight source 140 is the longest.

As the distance from the light source 140 decreases, scattering timebecomes shorter. In the example of FIG. 13, time for which each area isdriven is the same during the main lighting period. That is to say, timefor which Vch1 through Vch10 are applied to the areas CH1 through CH10,respectively, are the same. Time distribution is set during theluminance increase period so that time for which Vch1 is applied to thearea CH1 most distant from the light source 140 is longest and so thatas the distance from the light source 140 decreases, time for which adrive voltage is applied will become shorter.

In the above way, by controlling a voltage applied to area electrodescorresponding to an area, control is exercised so as to put the areainto the scattering state or the transmission state.

By the way, in the example of FIG. 11, image scanning is performed fromthe area CH1 distant from the light source 140. However, image scanningmay be begun at the area CH10 near the light source 140. In this case,backlight scanning by the PDLC driver 116 is also begun at the areaCH10. FIG. 14 illustrates another example of a drive pattern of thedisplay device according to the second embodiment. FIG. 14 is the sameas FIG. 11 with the exception that scanning order is reversed.

In the example of FIG. 14, the display driver 114 performs imagescanning in order from the area CH10 nearest the light source 140 to thearea CH1 during an image scanning period. The PDLC driver 116 performsbacklight scanning in synchronization with the image scanning. In theexample of FIG. 14, after the display driver 114 ends image scanning onthe area CH10, the PDLC driver 116 exercises control so as to put thearea CH10 into the scattering state during scanning period ts of thenext area CH9. Similarly, after the display driver 114 ends imagescanning on each of the areas CH9 through CH1 in order, the PDLC driver116 exercises control so as to put the area into the scattering stateduring scanning period ts of the next area. In this way, control isexercised during a main lighting period so as to put the areas CH10through CH1 into the scattering state during the scanning period ts.

The drive pattern determination block 155 determines a drive pattern toincrease the luminance of each area during a luminance increase period.In the example of FIG. 14, a drive pattern for making the luminance ofall the areas uniform is determined with the luminance of the area CH10nearest the light source 140 as reference. This is the same with theexample of FIG. 11. With the drive pattern illustrated in FIG. 14,scattering time tb9 of the area CH9 nearest the light source 140 next tothe area CH10 is the shortest and scattering time is increased accordingto the distance from the light source 140 from scattering time tb8 ofthe area CH8 to scattering time tbl of the area CH1. The PDLC driver 116exercises control on the basis of the drive pattern so as to put theareas CH10 through CH1 into the scattering state in order. By doing so,luminance is increased.

The PDLC driver 116 exercises control during the luminance increaseperiod so as to put the areas CH10 through CH1 into the scattering statein that order for scattering time corresponding the distance from thelight source 140. Even if image scanning is performed in this order, thePDLC 1331 is put into the scattering state after the image scanningends. This makes it possible to perform a local dimming process withoutusing a frame memory.

After image scanning on an area ends, the backlight in the area is lit.This makes it possible not only to perform a local dimming processwithout using a frame memory but also to suppress deterioration in imagequality. If image scanning and backlight scanning are performed on thesame area at the same time, then a screen in a state in which an imagein the area is not completely switched to a new image is visuallyrecognized. By performing backlight scanning after the end of imagescanning, the backlight is lit in a state in which an image signalcorresponding to an area is updated. As a result, a user visuallyrecognizes an updated screen. In addition, the backlight is lit in anarea only for time in a main lighting period and a luminance increaseperiod assigned to the area. The backlight is unlit during the remainingperiod. As a result, a moving image blur caused by hold display isreduced.

In the above first and second embodiments a case where a light source isdisposed on one side in the direction in which areas after division aredisposed is described. When an electric field is not applied, PDLC is inthe transmission state. Light which enters an area travels in a lighttraveling direction to the next area. When an area is put into thescattering state, control is exercised so as to put the other areas intothe transmission state. Therefore, in the first and second embodimentslight which enters from a side on which a light source is not disposedalso travels to an area in the scattering state. In this way, lightwhich enters from an opposite side is also used. An embodiment in whichtwo light sources are disposed will now be described.

(Third Embodiment)

A third embodiment will be described. FIG. 15 illustrates an example ofthe structure of a display device according to a third embodiment. Adisplay device 20 according to a third embodiment has a structure inwhich the light source 6 and the controller 7 included in the displaydevice 1 according to the first embodiment illustrated in FIG. 1 arereplaced with a first light source 61 and a second light source 62 and acontroller 71 respectively. Components in FIG. 15 which are the same asthose illustrated in FIG. 1 are marked with the same numerals anddescriptions of them will be omitted.

The first light source 61 is disposed near a first side of a lightmodulation layer 4 and emits light. This light enters the lightmodulation layer 4 from the first side and travels in the lightmodulation layer 4. As illustrated in FIG. 7, with the intensity oflight from the first light source 61 which enters an area 4 d asreference, the intensity of the light which enters areas 4 c, 4 b, and 4a decreases in that order. The first light source 61 is coupled to thecontroller 71. The controller 71 on-off controls light emission andcontrols the amount of light at light emission time.

The second light source 62 is disposed near a second side opposite thefirst side and emits light. This light enters the light modulation layer4 from the second side and travels in the light modulation layer 4.Light from the first light source 61 and light from the second lightsource 62 travel in opposite directions. With the intensity of lightfrom the second light source 62 which enters the area 4 a as reference,the intensity of the light which enters the areas 4 b, 4 c, and 4 ddecreases in that order. The second light source 62 is coupled to thecontroller 71. The controller 71 on-off controls light emission andcontrols the amount of light at light emission time.

The controller 71 controls in synchronization with the frame cycle of animage display panel 2 driving of the areas between partial electrodes 3a, 3 b, 3 c, and 3 d and a corresponding second electrode 5 and drivingof the first light source 61 and the second light source 62. Thecontroller 71 is, for example, a processor such as a CPU. The controller71 selects the areas 4 a, 4 b, 4 c, and 4 d in determined order everyframe cycle and performs backlight scanning. At this time the controller71 controls a first electrode 3, the second electrode 5, the first lightsource 61, and the second light source 62 according to the distancebetween a selected area and the first light source 61 and the distancebetween the selected area and the second light source 62 so that theselected area will obtain desired required luminance.

An example of the operation of the display device 20 will be described.

The display device 20 performs image scanning and backlight scanningevery frame cycle. Image scanning on the image display panel 2 isperformed in the order of display areas 2 a, 2 b, 2 c, and 2 d or in thereverse order. The controller 71 selects the areas 4 a, 4 b, 4 c, and 4d in the order in which image scanning is performed, and exercisescontrol so as to put a selected area into the scattering state. At thistime the amount of a decrease in the intensity of light from the firstlight source 61 which enters the area 4 a, 4 b, 4 c, or 4 d depends onthe distance from the first side. Similarly, the amount of a decrease inthe intensity of light from the second light source 62 which enters thearea 4 a, 4 b, 4 c, or 4 d depends on the distance from the second side.Accordingly, the amount of a decrease in the intensity of light from thefirst light source 61 and light from the second light source 62 whichenter the area 4 a, 4 b, 4 c, or 4 d is calculated on the basis of thedistance from the first side and the distance from the second side. Thecontroller 71 controls the first light source 61, the second lightsource 62, the first electrode 3, and the second electrode 5 so as tocorrect the amount of a decrease in the intensity of light in the area 4a, 4 b, 4 c, or 4 d. For example, the controller 71 lights both of thefirst light source 61 and the second light source 62 to increase theluminance of light which enters the area 4 a, 4 b, 4 c, or 4 d. Thecontroller 71 may control a light source current of the first lightsource 61 or the second light source 62 to increase the intensity oflight emitted from at least one of them. The controller 71 may adjustscattering time of the area 4 a, 4 b, 4 c, or 4 d. The controller 71controls at least one of the first light source 61, the second lightsource 62, and the partial electrodes 3 a, 3 b, 3 c, and 3 d so that theareas 4 a, 4 b, 4 c, and 4 d will realize desired luminance.

The controller 71 may select the area 4 a, 4 b, 4 c, or 4 dcorresponding to the display area 2 a, 2 b, 2 c, or 2 d on which imagescanning has ended, and perform backlight scanning. Backlight scanningon the same area is delayed until the time when image scanning ends. Bydoing so, a required luminance value of a backlight is calculated beforethe backlight scanning by the use of an image signal used for the imagescanning. This makes it possible to perform a local dimming processwithout using a frame memory. Furthermore, as with the secondembodiment, deterioration in image quality, such as a moving image blur,is suppressed.

As has been described, the display device 20 controls at least one ofscattering time of the areas 4 a, 4 b, 4 c, and 4 d, on-off of the firstlight source 61 and the second light source 62, and the amounts of lightemitted from the first light source 61 and the second light source 62 onthe basis of luminance corresponding to the distance from the firstlight source 61 and the distance from the second light source 62. Thismakes it possible to uniformize the luminance of the areas 4 a, 4 b, 4c, and 4 d regardless of the distance from the first light source 61 andthe distance from the second light source 62.

(Fourth Embodiment)

A display device according to a fourth embodiment will be described.FIG. 16 is a perspective view illustrative of the structure of a displaydevice according to a fourth embodiment. A display device 200 accordingto a fourth embodiment includes a second light source 242 in addition toa first light source 241 disposed at the same position where the lightsource 140 of the display device 100 according to the second embodimentillustrated in FIG. 2 is disposed. Components in FIG. 16 which are thesame as those illustrated in FIG. 2 are marked with the same numeralsand descriptions of them will be omitted.

With the display device 200 according to the fourth embodiment the firstlight source 241 and the second light source 242 are disposed near afirst side and a second side, respectively, opposite each other of sidesof a light guide section 130 parallel to a direction in which an LCDpanel 120 is stacked on the light guide section 130.

The first light source 241 is disposed near the first side and emitslight. This light travels in the light guide section 130. In the exampleof FIG. 16, the first light source 241 is disposed near an area CH10.Light from the first light source 241 which enters the light guidesection 130 travels in the light guide section 130 from the area CH10 toan area CH1. Furthermore, as the light travels further in the lightguide section 130, the intensity of the light decreases from theintensity at the time of the light entering the light guide section 130from the first side. The intensity of light emitted from the first lightsource 241 is controlled by a light source current supplied to the firstlight source 241.

The second light source 242 is disposed near the second side and emitslight. This light travels in the light guide section 130. In the exampleof FIG. 16, the second light source 242 is disposed near the area CH1.Light from the second light source 242 which enters the light guidesection 130 travels in the light guide section 130 from the area CH1 tothe area CH10. As the light travels further in the light guide section130, the intensity of the light decreases from the intensity at the timeof the light entering the light guide section 130 from the second side.The intensity of light emitted from the second light source 242 iscontrolled by a light source current supplied to the second light source242.

The light guide section 130, together with the first light source 241and the second light source 242, makes up a backlight.

For convenience, it is assumed in the following description that adirection in which the first light source 241 and the second lightsource 242 are disposed is an X direction, that a direction in whichlight from the first light source 241 travels is a Y direction, and thata direction in which the light guide section 130 and the LCD panel 120are stacked is a Z direction.

Next, the structure of the light guide section 130 will be described.FIG. 17 is a sectional view illustrative of an example of the structureof the light guide section of the display device according to the fourthembodiment. FIG. 17 is a sectional view taken along the line B-B′ ofFIG. 16. Components in FIG. 17 which are the same as those illustratedin FIG. 3 are marked with the same numerals and descriptions of themwill be omitted.

The first light source 241 is disposed near the first side of the lightguide section 130. The first light source 241 is a linear light sourceextending in the X direction of the light guide section 130 (see FIG.16), and emits a uniform light toward the light guide section 130. Forexample, the first light source 241 is formed by arranging LEDs in a rowin the X direction. If light emitted from the first light source 241 isnot scattered in a PDLC layer 133, then the light travels in the PDLClayer 133 in the order of the areas CH10 through CH1.

The second light source 242 is disposed near the second side of thelight guide section 130. The second light source 242 is a linear lightsource extending in the X direction of the light guide section 130 (seeFIG. 16), and emits a uniform light toward the light guide section 130.If light emitted from the second light source 242 is not scattered inthe PDLC layer 133, then the light travels in the PDLC layer 133 in theorder of the areas CH1 through CH10.

In this way, light emitted from the first light source 241 and lightemitted from the second light source 242 travel in opposite directionsin the PDLC layer 133.

The first light source 241 and the second light source 242 arecontrolled individually.

PDLC 1331 of the display device 200 has the characteristics illustratedin FIGS. 4A and 4B. The PDLC 1331 in an area is switched to thescattering state or the transmission state by controlling a voltageapplied to area electrodes formed in the area. The PDLC 1331 of thedisplay device 200 goes into the scattering state when a drive voltageis applied to area electrodes to generate an electric field.Furthermore, the PDLC 1331 of the display device 200 goes into thetransmission state when a drive voltage is not applied to areaelectrodes and an electric field is not generated. For example, an upperelectrode 134 and a lower electrode 135 which make up area electrodeshave the structures illustrated in FIG. 5.

Furthermore, the hardware configuration of the display device 200 is thesame as that of the display device 100 illustrated in FIG. 8. That is tosay, the display device 200 has a control unit 110 including a CPU 111,a RAM 112, a ROM 113, and the like. The control unit 110 controls thewhole of the display device 200. A display driver 114 which drives theLCD panel 120, a light source driver 115 which drives the first lightsource 241 and the second light source 242, and a PDLC driver 116 whichdrives area electrodes used for driving the PDLC 1331 of the light guidesection 130 are coupled to the control unit 110 via a bus 119. Thecontrol unit 110 outputs instructions to a driver. By doing so, the LCDpanel 120, the first light source 241, the second light source 242, orarea electrodes are controlled.

FIG. 18 illustrates the luminance distribution of light from the lightsources of the display device according to the fourth embodiment. FIG.18 is a plan view of the light guide section 130, the first light source241, and the second light source 242 from the Z direction (see FIG. 16)and a graph indicative of the luminance of each area. A dotted line onthe graph indicates the boundary between areas.

Each of the first light source 241 and the second light source 242 emitsa uniform light from a side opposite the light guide section 130 towardthe light guide section 130. Furthermore, the intensity of light emittedfrom at least one of the first light source 241 and the second lightsource 242 is controlled by controlling a drive current.

Hereinafter it is assumed that the luminance of the first light source241 is uniform in the X direction. Furthermore, for example, the amountof light emitted may be controlled for each LED in the first lightsource 241 made up of a plurality of LEDs. The above description alsoapplies to the second light source 242.

As illustrated in FIG. 18, as light from the first light source 241travels further in the PDLC layer 133 from the area CH10 to the areaCH1, its luminance decreases. On the other hand, light emitted from thesecond light source 242 enters the PDLC layer 133 from the second sideof the light guide section 130 opposite the first light source 241. Asthe light emitted from the second light source 242 travels further inthe PDLC layer 133 in a direction reverse to the direction in which thelight from the first light source 241 travels, its luminance decreases.In the example of FIG. 18, it is assumed that the intensity of lightemitted from the first light source 241 and the intensity of lightemitted from the second light source 242 are the same. That is to say,the intensity of light from the first light source 241 at the time ofentering the PDLC layer 133 from the first side and the intensity oflight from the second light source 242 at the time of entering the PDLClayer 133 from the second side are the same.

In FIG. 18, the intensity of light from the first light source 241 ineach area is indicated by a thick dotted line. The intensity of lightfrom the first light source 241 which enters the light guide section 130decreases as the distance from the first side increases, with theintensity of the light from the first light source 241 at the time ofentering the PDLC layer 133 from the first side as reference. Theintensity of light from the first light source 241 which enters eacharea is as follows: CH10>CH9>CH8>CH7>CH6>CH5>CH4>CH3>CH2>CH1.

Furthermore, the intensity of light from the second light source 242 ineach area is indicated by a dot-dash line. The intensity of light fromthe second light source 242 which enters the light guide section 130decreases as the distance from the second side increases, with theintensity of the light from the second light source 242 at the time ofentering the PDLC layer 133 from the second side as reference. Theintensity of light from the second light source 242 which enters eacharea is as follows: CH1>CH2>CH3>CH4>CH5>CH6>CH7>CH8>CH9>CH10.

Total intensity indicates luminance obtained by totalizing the intensityof the light from the first light source 241 which enters an area andthe intensity of the light from the second light source 242 which entersthe area. In FIG. 18, the total intensity is indicated by a solid line.If the luminance distribution of the first light source 241 and theluminance distribution of the second light source 242 illustrated inFIG. 18 are obtained, then the total luminance becomes lower in acentral area which occupies an intermediate position between the firstlight source 241 and the second light source 242.

If the intensity of light from the first light source 241 and theintensity of light from the second light source 242 differ, then thedistribution of total intensity differs from that of the total intensityillustrated in FIG. 18. In this case, total intensity is also obtainedby totalizing the luminance distribution of the first light source 241alone and the luminance distribution of the second light source 242alone.

FIG. 19 illustrates an example of the structure of the functions of thedisplay device according to the fourth embodiment. Components in FIG. 19which are the same as those of the display device 100 illustrated inFIG. 9 are marked with the same numerals and descriptions of them willbe omitted.

With the display device 200 a signal processing section 250 acceptsimage signals in order, generates display signals, and drives a displaydriver 114. Furthermore, the signal processing section 250 generates adrive pattern used for backlight scanning on the basis of an imagesignal and uses the drive pattern for driving a light source driver 215and a PDLC driver 116.

The light source driver 215 is coupled to the first light source 241 andthe second light source 242. The light source driver 215 controls alight source current supplied to the first light source 241 on the basisof a drive pattern to control the intensity of light from the firstlight source 241 which enters the PDLC layer 133. Furthermore, the lightsource driver 215 controls a light source current supplied to the secondlight source 242 on the basis of the drive pattern to control theintensity of light from the second light source 242 which enters thePDLC layer 133. Individual light source drivers 215 may be used for thefirst light source 241 and the second light source 242.

An example of the signal processing section 250 will be described. Thesignal processing section 250 includes an image processing block 151, atiming generation block 152, an image analysis block 153, a light sourcedata storage block 254, and a drive pattern determination block 255. Theimage processing block 151, the timing generation block 152, the imageanalysis block 153, and the drive pattern determination block 255 arerealized by, for example, a processor such as the CPU. The light sourcedata storage block 254 is realized by a storage area secured in the RAM,the ROM, or the like.

Processes performed by the image processing block 151 which generates asignal for image scanning, the timing generation block 152 whichgenerates a timing signal for image scanning, and the image analysisblock 153 which analyzes an image signal corresponding to an area forcalculating a required luminance value are the same as those performedby the image processing block 151, the timing generation block 152, andthe image analysis block 153 illustrated in FIG. 9.

The light source data storage block 254 stores luminance distributiontables in which the luminance of the backlight is recorded forrespective areas. The light source data storage block 254 stores firstluminance distribution tables obtained at the time of lighting the firstlight source 241 alone and second luminance distribution tables obtainedat the time of lighting the second light source 242 alone. Furthermore,the light source data storage block 254 may store at need thirdluminance distribution tables obtained at the time of lighting both ofthe first light source 241 and the second light source 242.

With the first luminance distribution tables, for example, the firstlight source 241 is driven by a determined light source current and theareas are put into the scattering state under the same conditions. Forexample, the same conditions mean that the same voltage is applied toarea electrodes and that scattering time is the same. The luminance oflight emitted at this time from the areas is measured to draw up thefirst luminance distribution tables. Similarly, the second light source242 is driven by a determined light source current and the areas are putinto the scattering state under the same conditions. The luminance oflight emitted at this time from the areas is measured to draw up thesecond luminance distribution tables. Furthermore, at need, both of thefirst light source 241 and the second light source 242 are driven bydetermined light source currents and the areas are put into thescattering state under the same conditions. The luminance of lightemitted at this time from the areas is measured to draw up the thirdluminance distribution tables. In these luminance distribution tables,for example, measured luminance of the areas is associated with theareas.

The drive pattern determination block 255 determines a drive pattern ofan area on the basis of a required luminance value acquired from theimage analysis block 153 and a luminance distribution table. The drivepattern controls at least one of, for example, a light source currentfor driving the first light source 241, a light source current fordriving the second light source 242, scattering time during which thePDLC driver 116 drives area electrodes in a target area, and a drivevoltage applied to the area electrodes.

FIG. 20 illustrates partial drive of the backlight in the display deviceaccording to the fourth embodiment. In FIG. 20, light L5 from the firstlight source 241 which enters the PDLC layer 133 is indicated by a thickdotted line and light L6 from the second light source 242 which entersthe PDLC layer 133 is indicated by a dot-dash line.

If the light L5 is not scattered in the PDLC layer 133, the light L5travels in the Y direction from the area CH10 to the area CH1 whilebeing totally reflected by the transparent substrates 131 and 132. Ifthe light L6 is not scattered in the PDLC layer 133, the light L6travels in a direction from the area CH1 to the area CH10 reverse to theY direction while being totally reflected by the transparent substrates131 and 132. The light L5 and the light L6 travel straight in a spacer1332.

A drive voltage is applied to area electrodes in the area CH7 and thearea CH7 is put into the scattering state. At this time the other areasare put into the transmission state. The light L5 travels in the areasCH10, CH9, and CH8 in the transmission state and enters the area CH7.Because the area CH7 is in the scattering state, the light L5 isscattered. On the other hand, the light L6 travels in the areas CH1,CH2, CH3, CH4, CH5, and CH6 in the transmission state and enters thearea CH7. Because the area CH7 is in the scattering state, the light L6is scattered. The light L5 emitted from the first light source 241 andthe light L6 emitted from the second light source 242 are scattered inthe area CH7 and part of the light L5 and the light L6 is emitted towardthe LCD panel 120. Light which travels to the transparent substrate 132side is returned into the PDLC 1331 by a reflection sheet 138. At thistime it is visually recognized from the LCD panel 120 side that thelight guide section 130 is in a state in which the area CH7 is luminousand in which the other areas are not luminous.

In this way, light emitted from the first light source 241 and lightemitted from the second light source 242 are scattered by putting theareas into the scattering state in order. By doing so, backlightscanning is performed. Because light from two light sources is used,luminance is increased compared with a case where one light source isused.

In the fourth embodiment, in order to uniformize the luminance of thebacklight, scattering time is uniformly distributed to the areas anddrive currents of the first light source 241 and the second light source242 are controlled. In the following description the first light source241 and the second light source 242 are also indicated by LS1 and LS2respectively.

(1) FIRST EXAMPLE

In a first example, a drive current of the second light source 242 iscontrolled to uniformize the luminance of the backlight.

FIG. 21 illustrates a first example of a drive pattern of the displaydevice according to the fourth embodiment. In FIG. 21, a column in thevertical direction indicates the areas CH1 through CH10 and a row in thehorizontal direction indicates time elapsed. This is the same with FIG.11. Each time zone corresponding to the areas CH1 through CH10 in whichnothing is stated is a period during which a corresponding area is inthe transmission state. Furthermore, each time zone indicated by obliquelines is a period during which a corresponding area is driven so as tobe in the scattering state. Moreover, a thick dotted line indicatesimage scanning is indicates time taken to perform image scanning on onearea. td indicates a drive period assigned to each area in a backlightscanning period. Area electrodes are controlled in a drive period sothat an area will be in the scattering state. Scattering time of an areain a drive period is properly controlled with the drive period as amaximum. In the first example, the backlight scanning period isuniformly distributed to all the areas and the drive period td isassigned to each area.

An LS1 current indicates a light source current supplied to the firstlight source 241. An LS2 current indicates a light source currentsupplied to the second light source 242.

In FIG. 21, an LS2 current i21 indicates the value of a current suppliedto the second light source 242 for a period for which the area CH1 isput into the scattering state. Similarly, it is assumed that the valuesof LS2 currents supplied to the second light source 242 during driveperiods of the areas CH2, CH3, CH4, CH5, CH6, CH7, CH8, CH9, and CH10are i22, i23, i24, i25, i26, i27, i28, i29, and i210 respectively. Thevalue of an LS1 current i11 supplied to the first light source 241 isconstant.

In the fourth embodiment, a frame period is uniformly distributed to theareas CH1 through CH10 to set drive periods. Backlight scanning andimage scanning are performed in the same direction. Furthermore, thebacklight scanning is begun after the image scanning on the first areaends.

As long as the image scanning and the backlight scanning are performedin the same direction, scanning may be performed from the area CH10 tothe area CH1.

If the intensity of light emitted from the first light source 241 andthe intensity of light emitted from the second light source 242 are thesame as illustrated in FIG. 18, then total intensity obtained bytotalizing the intensity of the light emitted from the first lightsource 241 and the intensity of the light emitted from the second lightsource 242 becomes lower in a central area which occupies anintermediate position between the first light source 241 and the secondlight source 242. In the example of FIG. 18, the total luminance islowest in the areas CH5 and CH6.

With the drive pattern in the first example an LS2 current of the secondlight source 242 is increased during drive periods of the central areasin which the total luminance decreases. In FIG. 21, the drive pattern isset on the basis of the amount of a decrease in the total luminance tosatisfy i25>i24>i23>i22>i21, in which the LS2 current i25 is largest.Similarly, the drive pattern is set on the basis of the amount of adecrease in the total luminance to satisfy i26>i27>i28>i29>i210, inwhich the LS2 current i26 is largest. The total intensity of light fromthe first light source 241 which enters an area and light from thesecond light source 242 which enters the area decreases as the distancefrom the first light source 241 and the distance from the second lightsource 242 increase. The amount of the decrease in the total intensityis corrected by increasing the luminance of the second light source 242.As a result, the luminance of the backlight is uniformized in all theareas.

The image scanning is not synchronized with the backlight scanning.However, an image scanning period assigned to an area is shorter than abacklight scanning period. The reason for this is as follows. Full timecorresponding to one frame is used as a backlight scanning period. Onthe other hand, an image scanning period is time obtained by subtractinga vertical blanking period from time corresponding to one frame.Therefore, at the time when the backlight scanning is begun, the imagescanning on a target area has ended. As a result, before the backlightscanning is begun, a drive pattern based on an image signal iscalculated. Accordingly, with the display device according to the fourthembodiment it is possible to perform a local dimming process withoutusing a frame memory.

FIGS. 22A and 22B illustrate the luminance distribution of the backlightin the first example of a drive pattern of the display device accordingto the fourth embodiment.

Corrected LS2 luminance distribution in FIG. 22A describes the luminancedistribution of the second light source (LS2) after a correction at thetime of performing backlight scanning on the basis of the drive patternin the first example.

LS1 luminance distribution is the luminance distribution of thebacklight during a frame period at the time of driving each area underthe same conditions with an LS1 current supplied to the first lightsource 241 constant. LS2 luminance distribution is the luminancedistribution of the backlight during the frame period at the time ofdriving each area under the same conditions with an LS2 current suppliedto the second light source 242 constant. If all the areas are drivenunder the same conditions, light which enters is scattered in the sameway. Accordingly, the same luminance distribution that is illustrated inFIG. 18 is obtained.

The corrected LS2 luminance distribution indicates the luminancedistribution of the backlight obtained at the time of driving the secondlight source 242 on the basis of the drive pattern in the first example.As illustrated in FIG. 18, if the LS1 luminance distribution and the LS2luminance distribution are totalized, the total intensity of light whichenters the areas CH5 and CH6 which occupy an intermediate positionbetween the first light source 241 and the second light source 242decreases. With the drive pattern in the first example the LS2 currentsi25 and i26 supplied during the drive periods of the areas CH5 and CH6in which the total luminance decreases are made larger than an LS2current supplied during a drive period of another area. As a result, asindicated by the corrected LS2 luminance distribution, the intensity ofbacklight light based on the second light source 242 is increased in theareas CH5 and CH6.

Total luminance distribution in FIG. 22B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the first example. By totalizing thecorrected LS2 luminance distribution after the correction and the LS1luminance distribution, the total luminance distribution which isuniform in all the areas is obtained.

(2) SECOND EXAMPLE

In a second example, a drive current of the first light source 241 iscontrolled to uniformize the luminance of the backlight.

FIG. 23 illustrates a second example of a drive pattern of the displaydevice according to the fourth embodiment. The same names are given toelements in FIG. 23 which are the same as those in FIG. 21 anddescriptions of them will be omitted. Furthermore, a time zonecorresponding to an area in which nothing is stated is a period duringwhich the area is in the transmission state. Moreover, a time zoneindicated by oblique lines is a period during which a corresponding areais driven so as to be in the scattering state. In addition, a thickdotted line indicates image scanning. These are the same with FIG. 21.

In the second example, a drive current of the first light source 241 iscontrolled. Backlight scanning is performed in the same way as with thefirst example. With the drive pattern in the second example an LS1current of the first light source 241 is increased during periods duringwhich backlight scanning is performed on the central areas in which thetotal luminance decreases. In FIG. 23, the drive pattern is set on thebasis of the amount of a decrease in the total luminance to satisfyi15>i14>i13>i12>i11, in which the LS1 current i15 is largest. Similarly,the drive pattern is set on the basis of the amount of a decrease in thetotal luminance to satisfy i16>i17>i18>i19>i110, in which the LS1current i16 is largest. The total intensity of light from the firstlight source 241 which enters an area and light from the second lightsource 242 which enters the area decreases as the distance from thefirst light source 241 and the distance from the second light source 242increase. The amount of the decrease in the total intensity is correctedby an LS1 current of the first light source 241. As a result, theluminance of the backlight is uniformized in all the areas.

FIGS. 24A and 24B illustrate the luminance distribution of the backlightin the second example of a drive pattern of the display device accordingto the fourth embodiment.

Corrected LS1 luminance distribution in FIG. 24A describes the luminancedistribution of the first light source 241 after a correction at thetime of performing backlight scanning on the basis of the drive patternin the second example. LS1 luminance distribution and LS2 luminancedistribution in FIG. 24A are the same as those in FIG. 22A.

The corrected LS1 luminance distribution indicates the luminancedistribution of the backlight obtained at the time of driving the firstlight source 241 on the basis of the drive pattern in the secondexample. With the drive pattern in the second example an LS1 current iscontrolled so as to make LS1 currents i15 and i16 corresponding to theareas CH5 and CH6 in which the total luminance decreases largest. As aresult, as indicated by the corrected LS1 luminance distribution, theluminance of the backlight based on the first light source 241 isincreased in the areas CH5 and CH6.

Total luminance distribution in FIG. 24B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the second example. By totalizing thecorrected LS1 luminance distribution after the correction and the LS2luminance distribution, the total luminance distribution which isuniform in all the areas is obtained.

(3) THIRD EXAMPLE

In a third example, an LS1 current of the first light source 241 and anLS2 current of the second light source 242 are controlled to uniformizethe luminance of the backlight.

FIG. 25 illustrates a third example of a drive pattern of the displaydevice according to the fourth embodiment. The same names are given toelements in FIG. 25 which are the same as those in FIG. 21 anddescriptions of them will be omitted.

In the third example, an LS1 current of the first light source 241 andan LS2 current of the second light source 242 are controlled. Backlightscanning is performed in the same way as with the first example. Withthe drive pattern in the third example an LS1 current of the first lightsource 241 and an LS2 current of the second light source 242 areincreased during periods during which backlight scanning is performed onthe central areas in which the total luminance decreases.

As illustrated in FIG. 25, with the first light source 241 the drivepattern is set on the basis of the amount of a decrease in the totalluminance to satisfy i15>i14>i13>i12>i11, in which the LS1 current i15is largest. Similarly, the drive pattern is set on the basis of theamount of a decrease in the total luminance to satisfyi16>i17>i18>i19>i110, in which the LS1 current i16 is largest.

In addition, with the second light source 242 the drive pattern is seton the basis of the amount of a decrease in the total luminance tosatisfy i25>i24>i23>i22>i21, in which the LS2 current i25 is largest.Similarly, the drive pattern is set on the basis of the amount of adecrease in the total luminance to satisfy i26>i27>i28>i29>i210, inwhich LS2 current i26 is largest.

The total intensity of light from the first light source 241 whichenters an area and light from the second light source 242 which entersthe area decreases as the distance from the first light source 241 andthe distance from the second light source 242 increase. The amount ofthe decrease in the total intensity is corrected by controlling an LS1current of the first light source 241 and an LS2 current of the secondlight source 242. As a result, the luminance of the backlight isuniformized in all the areas. In the third example the amount of adecrease in the luminance of the backlight in an area is corrected bythe two light sources, that is to say, by the first light source 241 andthe second light source 242. This suppresses the amount of an increasein drive current per light source. Therefore, when a drive current isincreased, the load on each of the first light source 241 and the secondlight source 242 is reduced.

FIGS. 26A and 26B illustrate the luminance distribution of the backlightin the third example of a drive pattern of the display device accordingto the fourth embodiment.

Corrected LS1 luminance distribution and corrected LS2 luminancedistribution in FIG. 26A describe the luminance distribution of thefirst light source 241 after a correction and the luminance distributionof the second light source 242 after a correction, respectively, at thetime of performing backlight scanning on the basis of the drive patternin the third example. LS1 luminance distribution and LS2 luminancedistribution in FIG. 26A are the same as those in FIG. 22A.

The corrected LS1 luminance distribution indicates the luminancedistribution of the backlight obtained at the time of driving the firstlight source 241 on the basis of the drive pattern in the third example.With the drive pattern in the third example a drive current iscontrolled so as to make LS1 currents i15 and i16 supplied during driveperiods of the areas CH5 and CH6 in which the total luminance decreaseslargest. Furthermore, the corrected LS2 luminance distribution indicatesthe luminance distribution of the backlight obtained at the time ofdriving the second light source 242 on the basis of the drive pattern inthe third example. With the drive pattern in the third example an LS2current is controlled so as to make LS2 currents i25 and i26 suppliedduring the drive periods of the areas CH5 and CH6 in which the totalluminance decreases largest. An LS1 current of the first light source241 and an LS2 current of the second light source 242 are set so thatthe amount of a decrease in the luminance of the backlight will becorrected by both of them. As a result, as indicated by the correctedLS1 luminance distribution, the luminance of the backlight based on thefirst light source (LS1) 241 is increased in the areas CH5 and CH6.

Total luminance distribution in FIG. 26B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the third example. By totalizing thecorrected LS1 luminance distribution after the correction and thecorrected LS2 luminance distribution after the correction, the totalluminance distribution which is uniform in all the areas is obtained.

As illustrated in FIG. 18, a case where the first light source 241 andthe second light source 242 are equal in the relationship between theintensity of light which enters an area and the distance between thearea and the incident surface is described in the above examples. In theexample of FIG. 18, each of the luminance distribution of the firstlight source 241 and the luminance distribution of the second lightsource 242 is line-symmetric with respect to a boundary between theareas CH5 and CH6 in the middle of a display surface. With the displaydevice according to the fourth embodiment, however, the luminancedistribution of a light source is not limited to the above luminancedistribution. In the fourth embodiment, on the basis of the amount of adecrease in the luminance of the backlight in an area and the luminancedistribution of the backlight obtained at the time of driving a lightsource to be driven by supplying a determined drive current, a drivecurrent for correcting the amount of the decrease in the luminance ofthe backlight is calculated.

As has been described, in the first example, the second example, and thethird example, a drive current of a light source is controlled touniformize the luminance of the backlight. However, a drive pattern ofthe display device according to the fourth embodiment is not limited tothe above drive patterns. Embodiments in which display devices havingthe same structure as the display device according to the fourthembodiment has exercise backlight control by the use of other drivepatterns will be described below. Display devices according toembodiments described below have the same structure as the displaydevice 200 illustrated in FIG. 16 has. A first light source 241 and asecond light source 242 are disposed near sides of a light guide section130 opposite each other. Furthermore, the luminance distribution of thefirst light source 241, the luminance distribution of the second lightsource 242, and total luminance are the same as those indicated in FIG.18.

(Fifth Embodiment)

A display device according to a fifth embodiment will be described. In afifth embodiment, a drive period assigned to each area is controlled touniformize the luminance of a backlight.

FIG. 27 illustrates an example of a drive pattern of a display deviceaccording to a fifth embodiment. The same names are given to elements inFIG. 27 which are the same as those in FIG. 21 and descriptions of themwill be omitted. Furthermore, a time zone corresponding to an area inwhich nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21. As with FIG. 18, FIG. 27illustrates an example of a case where the total luminance of the firstlight source 241 and the second light source 242 becomes lower incentral areas which occupy an intermediate position between the firstlight source 241 and the second light source 242.

With the drive pattern in the fifth embodiment, backlight scanning andimage scanning are performed in the same direction. Furthermore, thevalue of an LS1 current ic1 for driving the first light source 241 andthe value of an LS2 current ic2 for driving the second light source 242are constant and a drive period td is controlled. td1 indicates a driveperiod assigned to an area CH1 in a backlight scanning period.Similarly, drive periods assigned to areas CH2, CH3, CH4, CH5, CH6, CH7,CH8, CH9, and CH10 are indicated by td2, td3, td4, td5, td6, td7, td8,td9, and td10 respectively. ts indicates time taken to perform imagescanning on one area. In the fifth embodiment, a drive period td duringwhich required luminance is obtained is determined on the basis of thetotal luminance of light which enters an area. Therefore, scatteringtime corresponds to a drive period.

As illustrated in FIG. 27, with the drive pattern in the fifthembodiment the drive period td5 of a central area in which the totalluminance of incident light decreases is set to a long period on thebasis of the amount of the decrease in the total luminance. With thedrive pattern in the fifth embodiment the drive periods td5 and td6 ofthe central areas CH5 and CH6 are made long to increase the luminance ofthe backlight. In FIG. 27, setting of a drive period of each area is asfollows: td5, td6>td4, td7>td3, td8>td2, td9>td1, td10.

In this way, the luminance of the backlight decreases as the distancefrom the first light source 241 and the distance from the second lightsource 242 increases. With the drive pattern in the fifth embodiment theamount of the decrease in the luminance of the backlight is corrected bya drive period assigned to each area. In the example of FIG. 27, driveperiods of the areas CH5 and CH6 in which the total luminance ofincident light is low are longer than a drive period of another area inwhich the total luminance of incident light is high. As has beendescribed, with the drive pattern in the fifth embodiment totalluminance during a frame period is uniformized by controlling a driveperiod assigned to an area.

FIGS. 28A and 28B illustrate the luminance distribution of the backlightin the display device according to the fifth embodiment.

Corrected LS1 luminance distribution and corrected LS2 luminancedistribution in FIG. 28A describe the luminance distribution of thefirst light source (LS1) after a correction and the luminancedistribution of the second light source (LS2) after a correction,respectively, at the time of performing backlight scanning on the basisof the drive pattern in the fifth embodiment.

LS1 luminance distribution is the luminance distribution of the areasobtained during a frame period at the time of driving the areas underthe same conditions with an LS1 current supplied to the first lightsource 241 constant. LS2 luminance distribution is the luminancedistribution of the areas obtained during the frame period at the timeof driving the areas under the same conditions with an LS2 currentsupplied to the second light source 242 constant.

Each of the corrected LS1 luminance distribution and the corrected LS2luminance distribution indicates the luminance distribution of thebacklight obtained at the time of driving the areas on the basis of thedrive pattern in the fifth embodiment so as to put the areas into thescattering state. As illustrated in FIG. 18, if the LS1 luminancedistribution and the LS2 luminance distribution are totalized, the totalluminance of light which enters the areas CH5 and CH6 which occupy anintermediate position between the first light source 241 and the secondlight source 242 decreases. With the drive pattern in the fifthembodiment drive periods are assigned so that scattering time of theareas CH5 and CH6 in which the total luminance decreases will be long.As a result, as indicated by total luminance distribution, the luminanceof the backlight in the areas CH5 and CH6 is increased.

The total luminance distribution in FIG. 28B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the fifth embodiment. By totalizingthe corrected LS1 luminance distribution after the correction and thecorrected LS2 luminance distribution after the correction, the totalluminance distribution which is uniform in all the areas is obtained.

(Sixth Embodiment)

A display device according to a sixth embodiment will be described. In asixth embodiment, time not used as scattering time of a drive periodassigned to each area is utilized to uniformize the luminance of abacklight.

FIG. 29 illustrates an example of a drive pattern of a display deviceaccording to a sixth embodiment. The same names are given to elements inFIG. 29 which are the same as those in FIG. 21 and descriptions of themwill be omitted. Furthermore, a time zone corresponding to an area inwhich nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21.

With the drive pattern in the sixth embodiment, an LS1 current of afirst light source 241 is ic1, an LS2 current of a second light source242 is ic2, and the values of ic1 and ic2 are constant. Furthermore,drive periods td are uniformly assigned to all areas. In this case, theluminance of light which enters an area has the characteristic indicatedin FIG. 18 if all of each drive period td is used as scattering time. Asa result, uniform luminance is not obtained. With the drive pattern inthe sixth embodiment scattering time of an area in which the luminanceof incident light is high is made shorter than scattering time ofanother area on the basis of the total luminance of the first lightsource 241 and the second light source 242 indicated in FIG. 18. In anarea whose scattering time is made short, (drive period)>(scatteringtime). This means that there is a period during which light emitted froma light source is not utilized. A period during which light emitted froma light source is not utilized is an idle period. With the drive patternin the sixth embodiment an idle period is assigned to an area in whichthe luminance of incident light is low to increase the luminance of thebacklight.

In the example of FIG. 29, idle periods of areas CH7, CH8, CH9, and CH10near the first light source 241 in which the luminance of incident lightis high are assigned to areas CH5 and CH6 in which the luminance ofincident light is low. With the drive pattern of FIG. 29 the idleperiods of the areas CH7, CH8, and CH9 are assigned to the area CH5.Similarly, the idle period of the area CH10 is assigned to the area CH6.In this way, by assigning the idle periods to the areas CH5 and CH6 inwhich the luminance of incident light is low, scattering time of theareas CH5 and CH6 is increased. As a result, the luminance of thebacklight in the areas CH5 and CH6 is increased.

(Seventh Embodiment)

A display device according to a seventh embodiment will be described. Ina seventh embodiment, backlight scanning is performed in synchronizationwith image scanning and a vertical blanking period is utilized. By doingso, the luminance of a backlight is uniformized.

FIG. 30 illustrates an example of a drive pattern of a display deviceaccording to a seventh embodiment. The same names are given to elementsin FIG. 30 which are the same as those in FIG. 21 and descriptions ofthem will be omitted. Furthermore, a time zone corresponding to an areain which nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21.

With the drive pattern in the seventh embodiment control is exercised soas to make the value of an LS1 current ic1 of a first light source 241and the value of an LS2 current ic2 of a second light source 242constant. A backlight scanning period includes a main lighting periodcorresponding to an image scanning period and a luminance increaseperiod corresponding to a vertical blanking period.

A period which is the same as an image scanning period is of each areais assigned as a drive period in the main lighting period. As a result,backlight scanning is performed in synchronization with image scanningduring the main lighting period.

Scattering time of each area is controlled during the luminance increaseperiod on the basis of the total intensity of incident light. The totalintensity of light which enters an area is determined by the intensityof light emitted from the first light source 241, the distance betweenthe area and a first side, the intensity of light emitted from thesecond light source 242, and the distance between the area and a secondside. The drive pattern illustrated in FIG. 30 is a drive pattern usedin the case of the total luminance of light which enters an areaindicating the luminance distribution of FIG. 18. Control is exercisedduring the luminance increase period so as to make scattering time ofareas CH5 and CH6 in which the total intensity of incident light is lowlong.

As has been described, control is exercised in the luminance increaseperiod on the basis of the distribution of the total intensity ofincident light so as to put the areas CH5 and CH6 in which the luminanceof the backlight is low into the scattering state. If the luminance ofthe backlight in an area obtained in the main lighting period does notreach the reference luminance of the backlight, then a drive period inthe luminance increase period is determined so as to make up for adeficiency. This makes it possible to uniformize the luminance of thebacklight in all the areas.

With the drive patterns in the fourth through seventh embodiments thefirst light source (LS1) 241 and the second light source (LS2) 242 arelit at the same time. Drive patterns in which the first light source(LS1) 241 and the second light source (LS2) 242 are properly selected torealize power saving will now be described.

(Eighth Embodiment)

A display device according to an eighth embodiment will be described. Inan eighth embodiment, one of a first light source 241 and a second lightsource 242 is selected and lit to uniformize the luminance of abacklight and realize power saving.

FIG. 31 illustrates an example of a drive pattern of a display deviceaccording to an eighth embodiment. The same names are given to elementsin FIG. 31 which are the same as those in FIG. 21 and descriptions ofthem will be omitted. Furthermore, a time zone corresponding to an areain which nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21.

With the drive pattern illustrated in FIG. 31, control is exercised soas to make the value of an LS1 current ic1 of the first light source 241and the value of an LS2 current ic2 of the second light source 242constant. Furthermore, a backlight scanning period is distributed so asto make, on the basis of the total luminance of light which enters eacharea, a drive period of an area in which total luminance is low long. Adrive period is scattering time. With the drive pattern illustrated inFIG. 31, a drive period td5 of a central area CH5 and a drive period td6of a central area CH6 are made long to uniformize the luminance of thebacklight. In this case, the second light source 242 is on and the firstlight source 241 is off, during drive periods of areas CH1 through CH5near the second light source 242. In addition, the first light source241 is on and the second light source 242 is off, during scattering timeof areas CH6 through CH10 near the first light source 241. As indicatedin FIG. 18, the intensity of light from the first light source 241 orthe second light source 242 which enters an area decreases with anincrease in the distance between the first light source 241 or thesecond light source 242 and the area. In this way, a light source isselected on the basis of the amount of a decrease in the intensity ofincident light corresponding to the distance between a target area and afirst side or a second side.

FIGS. 32A and 32B illustrate the luminance distribution of the backlightin the display device according to the eighth embodiment.

Corrected LS1 luminance distribution and corrected LS2 luminancedistribution in FIG. 32A describe the luminance distribution of thefirst light source (LS1) after a correction and the luminancedistribution of the second light source (LS2) after a correction,respectively, at the time of performing backlight scanning on the basisof the drive pattern in the eighth embodiment.

Each of LS1 luminance distribution and LS2 luminance distributionindicates the intensity distribution of light which enters each areawith the luminance distribution indicated in FIG. 18 and which isemitted via a PDLC layer 133 driven under the same conditions.

The corrected LS1 luminance distribution indicates the intensitydistribution of light from the first light source 241 emitted from anemission surface 139 as backlight light at the time of driving each areaon the basis of the drive pattern in the eighth embodiment so as to puteach area into the scattering state. The corrected LS2 luminancedistribution indicates the intensity distribution of light from thesecond light source 242 emitted from the emission surface 139 asbacklight light at the time of driving each area on the basis of thedrive pattern in the eighth embodiment so as to put each area into thescattering state.

Total luminance distribution in FIG. 32B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the eighth embodiment. By totalizingthe corrected LS1 luminance distribution after the correction and thecorrected LS2 luminance distribution after the correction, the totalluminance distribution which is uniform in all the areas is obtained.

With the drive pattern in the eighth embodiment, of the first lightsource 241 and the second light source 242, one nearer an area, that isto say, one the luminance of incident light from which is higher in anarea is selected and lit. Because the amount of a correctioncorresponding to the amount of a decrease in the intensity of lightwhich enters an area near a light source is small, light emissionefficiency is good. As a result, power consumption is low compared witha display device in which a light source is disposed only near one side.

When an area is in the scattering state, light which enters the area isscattered in all directions. Therefore, part of a scattered lighttravels in a light traveling direction to the next and later areas. Partof a scattered light which travels to the next and later areas will bereferred to as a leakage light. By driving an area which a leakage lightenters so as to put the area into the scattering state, the leakagelight is utilized as backlight light. As indicated in FIG. 18, theintensity of light which enters an area decreases as the distancebetween the area and a side increases. If areas are driven under thesame conditions, the luminance of the backlight in an area distant in alight traveling direction is low. Therefore, by utilizing a leakagelight, the luminance of the backlight is increased in a distant area inwhich the luminance of the backlight is low.

(Ninth Embodiment)

A display device according to a ninth embodiment will be described. Witha display device according to a ninth embodiment, a light source currentsupplied to a first light source 241 and a second light source 242 oneof which is lit is controlled to uniformize the luminance of abacklight.

FIG. 33 illustrates an example of a drive pattern of a display deviceaccording to a ninth embodiment. The same names are given to elements inFIG. 33 which are the same as those in FIG. 21 and descriptions of themwill be omitted. Furthermore, a time zone corresponding to an area inwhich nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21. With the drive pattern in theninth embodiment, a backlight scanning period is uniformly distributedto all areas to set drive periods td. Furthermore, on the basis of theintensity of light which enters an area, the first light source 241 orthe second light source 242 is selected and a light source current of aselected light source is controlled.

With the drive pattern illustrated in FIG. 33, the second light source242 is on and the first light source 241 is off, during scattering timeof areas CH1 through CH5 near the second light source 242. In addition,the first light source 241 is on and the second light source 242 is off,during scattering time of areas CH6 through CH10 near the first lightsource 241. This is the same with FIGS. 32A and 32B. Furthermore, withthe areas CH1, CH2, CH3, CH4, and CH5 for which the second light source242 is selected, the intensity of light from the second light source 242which enters each area decreases according to the distance from a secondside in the order of CH1>CH2>CH3>CH4>CH5. An LS2 current of the secondlight source 242 is increased to the amount of a decrease in theintensity of light from the second light source 242 in the order ofi21(CH1)<i22(CH2)<i23(CH3)<i24(CH4)<i25(CH5). i21 is an LS2 currentsupplied during the drive period of the area CH1. i22 through i25 arealso LS2 currents supplied during the drive periods of the areas CH2,CH3, CH4, and CH5 respectively. Similarly, an LS1 current of the firstlight source 241 is controlled on the basis of the intensity of lightfrom the first light source 241 which enters each area. An LS1 currentof the first light source 241 is decreased in the order ofi16(CH6)>i17(CH7)>i18(CH8)>i19(CH9)>i110(CH10). i16 is an LS1 currentsupplied during the drive period of the area CH6. i17 through i110 arealso LS1 currents supplied during the drive periods of the areas CH7,CH8, CH9, and CH10 respectively.

As has been described, on the basis of the amount of a decrease in theluminance of incident light corresponding to each of the distancebetween a target area and the first side and the distance between thetarget area and the second side, a light source is selected and a lightsource current is controlled. By doing so, the luminance of thebacklight is uniformized. By adopting the drive pattern illustrated inFIG. 33, the luminance distribution of the backlight and the effectindicated in FIGS. 32A and 32B are obtained.

By the way, there are cases where a luminance increase is performed in adisplay process by a LCD panel 120 to perform display with luminancehigher than luminance in normal display. By doing so, any portion of adisplayed image is highlighted. A drive pattern for performing aluminance increase will now be described.

(Tenth Embodiment)

A display device according to a tenth embodiment will be described. Witha display device according to a tenth embodiment, one of two lightsources is lit at normal time. This is the same with the eighthembodiment. When a luminance increase is performed, the two lightsources are lit at the same time during a drive period of a target areato increase the luminance of a backlight.

FIG. 34 illustrates an example of a drive pattern of a display deviceaccording to a tenth embodiment. The same names are given to elements inFIG. 34 which are the same as those in FIG. 21 and descriptions of themwill be omitted. Furthermore, a time zone corresponding to an area inwhich nothing is stated is a period during which the area is in thetransmission state. Moreover, a time zone indicated by oblique lines isa period during which a corresponding area is driven so as to be in thescattering state. In addition, a thick dotted line indicates imagescanning. These are the same with FIG. 21.

With the drive pattern illustrated in FIG. 34, a luminance increase isperformed on areas CH5 and CH6. Only a second light source 242 is litfor areas CH1, CH2, CH3, and CH4 and a drive period is controlledaccording to the distance between each area and a second side. This isthe same with the eighth embodiment. For the area CH5, a drive periodduring which the second light source 242 is lit is set on the basis ofthe distance between the area CH5 and the second side and a drive periodduring which a first light source 241 is lit is set. In order to scatterlight emitted from the second light source 242, the area CH5 is drivenduring its drive period so as to be in the scattering state. Inaddition, light emitted from the first light source 241 is scattered. Asa result, the luminance is increased. The amount of an increase in theluminance is controlled by time for which the first light source 241 islit and the value of an LS1 current. Similarly, for the area CH6, adrive period during which the first light source 241 is lit is set onthe basis of the distance between the area CH6 and a first side and adrive period during which the second light source 242 is lit is set. Theamount of an increase in the luminance is controlled by time for whichthe second light source 242 is lit and the value of an LS2 current.

FIGS. 35A and 35B illustrate the luminance distribution of the backlightin the display device according to the tenth embodiment.

Corrected LS1 luminance distribution and corrected LS2 luminancedistribution in FIG. 35A describe the luminance distribution of thefirst light source (LS1) after a correction and the luminancedistribution of the second light source (LS2) after a correction,respectively, at the time of performing backlight scanning on the basisof the drive pattern in the tenth embodiment.

The corrected LS1 luminance distribution indicates the intensitydistribution of light from the first light source 241 emitted from anemission surface 139 as backlight light at the time of driving each areaon the basis of the drive pattern in the tenth embodiment so as to puteach area into the scattering state. The corrected LS2 luminancedistribution indicates the intensity distribution of light from thesecond light source 242 emitted from the emission surface 139 asbacklight light at the time of driving each area on the basis of thedrive pattern in the tenth embodiment so as to put each area into thescattering state. The corrected LS1 luminance distribution is the sameas the corrected LS1 luminance distribution in FIG. 32A based on thedrive pattern in the eighth embodiment for the areas CH6 through CH10.An increase in the luminance is caused in the area CH5. The correctedLS2 luminance distribution is the same as the corrected LS2 luminancedistribution in FIG. 32A based on the drive pattern in the eighthembodiment for the areas CH1 through CH5. An increase in the luminanceis caused in the area CH6.

Total luminance distribution in FIG. 35B indicates the luminancedistribution of the backlight in each area after a correction made onthe basis of the drive pattern in the tenth embodiment. By totalizingthe corrected LS1 luminance distribution after the correction and thecorrected LS2 luminance distribution after the correction, the totalluminance distribution uniform in all the areas except the areas onwhich a luminance increase is performed is obtained. Luminance based onlight emitted from another lit light source is added to total luminancein the areas on which a luminance increase is performed to increase theluminance of the backlight.

With the drive pattern in the tenth embodiment, not only the same effectthat is obtained by the drive pattern in the eighth embodiment but alsoan increase in luminance in any area is realized. An area on which aluminance increase is performed and the amount of an increase inluminance are calculated by image analysis or the like.

(Eleventh Embodiment)

A display device according to an eleventh embodiment will be described.With a display device according to an eleventh embodiment, one of twolight sources is lit at normal time. This is the same with the ninthembodiment. When a luminance increase is performed, the two lightsources are lit at the same time during a drive period of a target areato increase the luminance of a backlight.

FIG. 36 illustrates an example of a drive pattern of a display deviceaccording to an eleventh embodiment. The same names are given toelements in FIG. 36 which are the same as those in FIG. 21 anddescriptions of them will be omitted. Furthermore, a time zonecorresponding to an area in which nothing is stated is a period duringwhich the area is in the transmission state. Moreover, a time zoneindicated by oblique lines is a period during which a corresponding areais driven so as to be in the scattering state. In addition, a thickdotted line indicates image scanning. These are the same with FIG. 21.In the example of FIG. 36, a luminance increase is performed on areasCH5 and CH6.

With the drive pattern illustrated in FIG. 36, a drive period isuniformly assigned to each area, as with the ninth embodiment, exceptthe areas on which a luminance increase is performed. A light sourcecurrent is controlled to uniformize luminance. As with the ninthembodiment, only a second light source 242 is lit for areas CH1, CH2,CH3, and CH4 and an LS2 current is controlled on the basis of thedistance between each area and the second light source 242. For the areaCH5, an LS2 current of the second light source 242 is set on the basisof the distance between the area CH5 and the second light source 242 anda first light source 241 is lit by supplying a determined LS1 current.Not only light emitted from the second light source 242 but also lightemitted from the first light source 241 is scattered during the driveperiod of the area CH5 to increase luminance. The amount of an increasein the luminance is controlled by the value of an LS1 current of thefirst light source 241. Similarly, during the drive period of the areaCH6, an LS1 current of the first light source 241 is set on the basis ofthe distance between the area CH6 and the first light source 241 and thesecond light source 242 is lit by supplying an LS2 current. The amountof an increase in luminance is controlled by the value of an LS2 currentof the second light source 242.

The luminance distribution of the backlight obtained at the time ofdriving each area on the basis of the drive pattern illustrated in FIG.36 is the same as the luminance distribution of the backlight in FIG. 35obtained at the time of driving each area on the basis of the drivepattern in the tenth embodiment.

With the drive pattern in the eleventh embodiment, not only the sameeffect that is obtained by the drive pattern in the ninth embodiment butalso an increase in luminance in any area is realized. An area on whicha luminance increase is performed and the amount of an increase inluminance are calculated by image analysis or the like.

(Twelfth Embodiment)

A display device according to a twelfth embodiment will be described. Inthe fourth through eleventh embodiments, scattering time of plural areasdoes not overlap. In a twelfth embodiment, however, control is exercisedso that scattering time of an area will coincide with scattering time ofanother area.

FIG. 37 illustrates partial drive of a backlight in a display deviceaccording to a twelfth embodiment.

In FIG. 37, light L7 from a first light source 241 which enters a PDLClayer 133 is indicated by a thick dotted line and light L8 from a secondlight source 242 which enters the PDLC layer 133 is indicated by adot-dash line.

If the light L7 is not scattered in the PDLC layer 133, the light L7travels in a Y direction from an area CH10 to an area CH1 while beingtotally reflected by transparent substrates 131 and 132. If the light L8is not scattered in the PDLC layer 133, the light L8 travels in adirection from the area CH1 to the area CH10 reverse to the Y directionwhile being totally reflected by the transparent substrates 131 and 132.The light L7 and the light L8 travel straight in a spacer 1332.

A drive voltage is applied to area electrodes in each of the area CH7and the area CH5 and the area CH7 and the area CH5 are put into thescattering state. At this time the other areas are put into thetransmission state. The light L7 travels in the areas CH10, CH9, and CH8in the transmission state and enters the area CH7. Because the area CH7is in the scattering state, the light L7 is scattered. On the otherhand, the light L8 travels in the areas CH1, CH2, CH3, and CH4 in thetransmission state and enters the area CH5. Because the area CH5 is inthe scattering state, the light L8 is scattered. Part of the light L7scattered in the area CH7 and part of the light L8 scattered in the areaCH5 are emitted toward a LCD panel 120. Light which travels to thetransparent substrate 132 side is returned into a PDLC 1331 by areflection sheet 138. At this time it is visually recognized from theLCD panel 120 side that a light guide section 130 is in a state in whichthe area CH7 and the area CH5 are luminous and in which the other areasare not luminous.

As has been described, light from the two light sources is utilized.This enables two areas to become luminous at the same time. If a firstarea is considered as reference, then a second area is selected fromamong areas from an area next to the first area to an area adjacent tothe second light source 242 in a direction in which light from the firstlight source 241 travels. In the example of FIG. 37, if the area CH7 isset as a first area, then a second area is selected from among the areasCH6 through CH1. A drive pattern in which two areas become luminous atthe same time will be described.

FIG. 38 illustrates an example of a drive pattern of the display deviceaccording to the twelfth embodiment. The same names are given toelements in FIG. 38 which are the same as those in FIG. 21 anddescriptions of them will be omitted. Furthermore, a time zonecorresponding to an area in which nothing is stated is a period duringwhich the area is in the transmission state. Moreover, a time zoneindicated by oblique lines is a period during which a corresponding areais driven so as to be in the scattering state. In addition, a thickdotted line indicates image scanning. These are the same with FIG. 21.With the drive pattern of the display device according to the twelfthembodiment, a first area in which light emitted from the first lightsource 241 is scattered and a second area in which light emitted fromthe second light source 242 is scattered are driven at the same time.

With the drive pattern illustrated in FIG. 38, the areas CH1 and CH2 areconsidered as one set, the areas CH3 and CH4 are considered as one set,the areas CH5 and CH6 are considered as one set, the areas CH7 and CH8are considered as one set, and the areas CH9 and CH10 are considered asone set. Control is exercised so that two areas will be in thescattering state at the same time. Furthermore, a backlight scanningperiod is uniformly distributed to these sets to set drive periods forall the areas. In addition, after image scanning on areas included in aset ends, backlight scanning is begun.

In the example of FIG. 38, at the time when image scanning (2ts) on aset of the areas CH1 and CH2 ends, the drive periods (2td) of the areasCH1 and CH2 are begun. 2ts indicates a period during which imagescanning on two areas is performed. 2td indicates that a period twice adrive period (td) per area obtained in the case of uniformlydistributing the backlight scanning period to all the areas is assigned.Furthermore, an LS1 current of the first light source 241 and an LS2current of the second light source 242 during a drive period of each setare controlled according to areas included in each set. With a set ofthe areas CH1 and CH2 light from the second light source 242 adjacent tothe area CH1 enters the area CH1. Accordingly, an LS2 current i21 issmall compared with an area included in another set. On the other hand,light from the first light source 241 distant from the area CH2 entersthe area CH2. Accordingly, an LS1 current i12 is large compared with anarea included in another set.

A set of the areas CH3 and CH4 is selected next to the set of the areasCH1 and CH2. A drive period assigned to the set of the areas CH3 and CH4is equal to that assigned to the set of the areas CH1 and CH2.Furthermore, because the area CH3 is more distant from the second lightsource 242 than the area CH1, an LS2 current i23 is larger than the LS2current i21. Because the area CH4 is nearer to the first light source241 than the area CH2, an LS1 current i14 is smaller than the LS1current i12. In this way, each set is selected in order and an LS1current and an LS2 current during a drive period are controlled.

FIG. 39 illustrates the luminance distribution of the backlight in thedisplay device according to the twelfth embodiment. FIG. 39 indicatestotal luminance distribution after a correction. LS1 indicates correctedluminance distribution of the backlight based on light from the firstlight source 241. LS2 indicates corrected luminance distribution of thebacklight based on light from the second light source 242.

The total luminance distribution is obtained by totalizing the correctedLS2 luminance distribution for the areas CH1, CH3, CH5, CH7, and CH9 andthe corrected LS1 luminance distribution for the areas CH2, CH4, CH6,CH8, and CH10.

As has been described, with the drive pattern in the twelfth embodimenttwo areas become luminous at the same time. As illustrated in FIG. 38, adrive period per area is doubled by causing two areas to become luminousat the same time. This increases the luminance of each area.

The drive patterns have been described. The above drive patterns may beused independently of one another or a combination of two or more ofthem may be used. For example, the drive pattern in which a drive periodassigned to an area is controlled according to the distance between thearea and a light source is adopted and control of a light source currentsupplied to the light source during the drive period of the area may beadded.

(Thirteenth Embodiment)

A display device according to a thirteenth embodiment will be described.In the fourth through twelfth embodiments, a frame memory is not used.In a thirteenth embodiment, however, a display device which includes aframe memory and which performs an image analysis on one screen will bedescribed.

FIG. 40 illustrates an example of the structure of the functions of adisplay device according to a thirteenth embodiment. Components in FIG.40 which are the same as those illustrated in FIG. 19 are marked withthe same numerals and descriptions of them will be omitted. A displaydevice 300 according to a thirteenth embodiment includes a frame memory351 in a signal processing section 350. An image analysis block 353analyzes an image stored in the frame memory 351.

The frame memory 351 stores image signals corresponding to at least oneframe inputted to the signal processing section 350. The frame memory351 is realized as a storage area secured in, for example, a RAM 112.

An image processing block 352 processes image signals stored in theframe memory 351 and outputs them to a display driver 114.

In a vertical blanking period, for example, the image analysis block 353analyzes image signals corresponding to one frame stored in the framememory 351 and draws up a luminance profile of a backlight. Theluminance profile is information obtained by calculating the luminanceof the backlight based on an image for each analysis unit such as area.

A drive pattern determination block 354 determines a drive pattern onthe basis of a luminance profile of the backlight corresponding to oneframe the image analysis block 353 draws up. The drive patterndetermination block 354 properly selects a drive pattern on the basis ofa luminance profile. The drive pattern determination block 354 selects adrive pattern which meets a predetermined condition, such as thecondition that power efficiency is best, and determines a first lightsource 241, a second light source 242, drive periods, and the like. Auser may set a condition in advance.

FIG. 41 illustrates drive timing of each functional section of thedisplay device according to the thirteenth embodiment. The same namesare given to elements in FIG. 41 which are the same as those in FIG. 10and descriptions of them will be omitted.

With the display device 300 image signals DE inputted to the signalprocessing section 350 are stored in order in the frame memory 351. Atthe time when an image scanning period in one frame ends, image signalscorresponding to the one frame are stored in the frame memory 351. In avertical blanking period, for example, the image analysis block 353analyzes the image signals stored in the frame memory 351 and draws up aluminance profile of the backlight. The drive pattern determinationblock 354 determines a drive pattern on the basis of the luminanceprofile and luminance distribution tables stored in a light source datastorage block 254. In the next frame period, the image processing block352 processes the image signals stored in the frame memory 351,generates display signals, and outputs the display signals to thedisplay driver 114. Furthermore, the drive pattern determination block354 controls a PDLC driver 116 and a light source driver 225 on thebasis of the determined drive pattern. The display driver 114, the PDLCdriver 116, and the light source driver 225 are driven on the basis of atiming signal generated by a timing generation block 152. The displaydriver 114 performs image scanning in synchronization with the timingsignal. The PDLC driver 116 and the light source driver 225 performbacklight scanning in synchronization with the timing signal. The PDLCdriver 116 drives area electrodes to put an area into the scatteringstate. Light which enters the area is scattered. The light source driver225 drives the first light source 241 and the second light source 242 tomake them emit light. The light enters the area.

Drive control exercised by drawing up a luminance profile will now bedescribed.

FIG. 42 illustrates an example of a display screen of the display deviceaccording to the thirteenth embodiment.

An image 600 is an example of an image displayed on a display screen ofa LCD panel 120. A portion of the image 600 indicated by oblique linesis a dark image. CH1, CH2, CH3, CH4, CH5, CH6, CH7, CH8, CH9, and CH10indicate areas of a light guide section 130.

In the example of FIG. 42, the dark image is displayed on a lowerportion of the screen corresponding to the areas CH6, CH7, CH8, CH9, andCH10. On the other hand, a bright image is displayed on an upper portionof the screen corresponding to the areas CH1, CH2, CH3, CH4, and CH5.Therefore, in a luminance profile of the backlight calculated by theimage analysis block 353, luminance is high in the areas CH1, CH2, CH3,CH4, and CH5 and luminance is low in the areas CH6, CH7, CH8, CH9, andCH10. On the basis of this luminance profile, the drive patterndetermination block 354 selects the drive pattern in the ninthembodiment illustrated in FIG. 33 as a drive pattern in which powerefficiency is best. With the drive pattern in the ninth embodiment, oneof the two light sources nearer an area is lit and a light sourcecurrent for driving the light source is controlled according to thedistance between the area and the light source.

FIG. 43 illustrates an example of a drive pattern of the display deviceaccording to the thirteenth embodiment. The same names are given toelements in FIG. 43 which are the same as those in FIG. 21 anddescriptions of them will be omitted. Furthermore, a time zonecorresponding to an area in which nothing is stated is a period duringwhich the area is in the transmission state. Moreover, a time zoneindicated by oblique lines is a period during which a corresponding areais driven so as to be in the scattering state. In addition, a thickdotted line indicates image scanning. These are the same with FIG. 21.

With the drive pattern illustrated in FIG. 43, only the second lightsource 242 is lit for the areas CH1, CH2, CH3, CH4, and CH5 near thesecond light source 242. On the other hand, only the first light source241 is lit for the areas CH6, CH7, CH8, CH9, and CH10 near the firstlight source 241. As described above with reference to the screen ofFIG. 42, the image in the upper portion corresponding to the areas CH1,CH2, CH3, CH4, and CH5 is brighter than that in the lower portioncorresponding to the areas CH6, CH7, CH8, CH9, and CH10, and thereforethe luminance of the areas CH1, CH2, CH3, CH4, and CH5 is higher thanthat of the areas CH6, CH7, CH8, CH9, and CH10 in the luminance profile.Since the luminance is high in the areas CH1, CH2, CH3, CH4, and CH5 inthe luminance profile, an LS2 current of the second light source 242 litduring drive periods assigned to these areas is increased. Furthermore,the distance from the second light source 242 increases in the order ofthe areas CH1, CH2, CH3, CH4, and CH5. Therefore, control is exercisedso that an LS2 current will increase in the order ofi21(CH1)<i22(CH2)<i23(CH3)<i24(CH4)<i25(CH5). On the other hand, asdescribed above with reference to the screen of FIG. 42, the image inthe lower portion corresponding to the areas CH6, CH7, CH8, CH9, andCH10 is darker than that in the upper portion corresponding to the areasCH1, CH2, CH3, CH4, and CH5, and therefore the luminance of the areasCH6, CH7, CH8, CH9, and CH10 is lower than that of the areas CH1, CH2,CH3, CH4, and CH5 in the luminance profile. Since the luminance is lowin the areas CH6, CH7, CH8, CH9, and CH10 in the luminance profile, anLS1 current of the first light source 241 lit during drive periodsassigned to these areas is set to a value lower than that of the LS2current. In addition, the distance from the first light source 241decreases in the order of the areas CH6, CH7, CH8, CH9, and CH10.Accordingly, control is exercised so that an LS1 current will decreasein the order of i16(CH6)>i17(CH7)>i18(CH8)>i19(CH9)>i110(CH10).

In this case, the following method may also be used. An LS1 current andan LS2 current are made constant and luminance is controlled bycontrolling lighting time for each area. This is the same with thesecond embodiment and the fifth through seventh embodiments.

FIG. 44 illustrates the luminance distribution of the backlight in thedisplay device according to the thirteenth embodiment. FIG. 44 indicatestotal luminance distribution after a correction. LS1 indicates correctedluminance distribution of the backlight based on light from the firstlight source 241. LS2 indicates corrected luminance distribution of thebacklight based on light from the second light source 242.

The total luminance distribution is obtained by totalizing the correctedLS2 luminance distribution for the areas CH1, CH2, CH3, CH4, and CH5 andthe corrected LS1 luminance distribution for the areas CH6, CH7, CH8,CH9, and CH10. With the drive pattern illustrated in FIG. 43, an LS1current for driving the first light source 241 is smaller than an LS2current for driving the second light source 242. In this way, on thebasis of a luminance profile, the value of a light source currentsupplied to a light source is set to a small value if high luminance isnot needed. As a result, light utilization efficiency is increased anddriving is performed by supplying low power. As has been described, bydrawing up a luminance profile before backlight scanning and determininga drive pattern on the basis of the luminance profile, a drive patternmore suitable for an image is generated.

The above processing functions can be realized with a computer. In thatcase, a program in which the contents of the functions that the displaydevice has are described is provided. By executing this program on thecomputer, the above processing functions are realized on the computer.This program may be recorded on a computer readable record medium. Acomputer readable record medium may be a magnetic storage device, anoptical disk, a magneto-optical recording medium, a semiconductormemory, or the like. A magnetic storage device may be a hard disk drive(HDD), a flexible disk (FD), a magnetic tape, or the like. An opticaldisk may be a digital versatile disc (DVD), a DVD-RAM, a compactdisc(CD)-ROM, a CD-recordable(R)/rewritable(RW), or the like. Amagneto-optical recording medium may be a magneto-optical disk (MO) orthe like.

To place the program on the market, portable record media, such as DVDsor CD-ROMs, on which it is recorded are sold. Alternatively, the programis stored in advance in a storage unit of a server computer and istransferred from the server computer to another computer via a network.

When a computer executes this program, it will store the program, whichis recorded on a portable record medium or which is transferred from theserver computer, in, for example, its storage unit. Then the computerreads the program from its storage unit and performs processes incompliance with the program. The computer may read the program directlyfrom a portable record medium and perform processes in compliance withthe program. Furthermore, each time the program is transferred from theserver computer connected via a network, the computer may performprocesses in order in compliance with the program it receives.

In addition, at least part of the above processing functions may berealized by an electronic circuit such as a digital signal processor(DSP), an ASIC, or a programmable logic device (PLD).

The present disclosure includes the following aspects.

(1) A display device including:

an image display panel which updates an image in a frame cycle includingan image scanning period and a vertical blanking period;

a light modulation layer disposed at a back of the image display paneland switched to a scattering state in which incident light is scatteredor a transmission state in which the incident light is transmittedaccording to an electric field applied;

a light source which emits light that enters the light modulation layerfrom a side thereof and travels in the light modulation layer;

electrodes which are formed according to divided areas of the lightmodulation layer arranged in a direction in which the light from thelight source travels and which apply the electric field to the lightmodulation layer; and

a controller which drives the electrodes in synchronization with imagescanning and switches in order the divided areas to be put into thescattering state, during a first period corresponding to the imagescanning period, and which drives the electrodes according to distancesfrom the side to control the scattering state according to the dividedareas, during a second period corresponding to the vertical blankingperiod.

(2) The display device according to (1), wherein the controller puts thedivided areas into the scattering state in an order in which the imagedisplay panel ends the image scanning.

(3) The display device according to (1), wherein the controller controlsscattering time for which the divided areas are put into the scatteringstate during the second period on the basis of amounts of decreases inluminances of the light from the light source which enters the lightmodulation layer from the side corresponding to distances to the dividedareas.

(4) The display device according to (1), wherein the controller controlsscattering time according to deficiencies when luminances of lightemitted from the divided areas in the first period do not reach requiredluminances on the basis of luminance distribution tables in whichluminances of light emitted from the divided areas when the dividedareas are put into the scattering state under same drive conditions areregistered.

(5) The display device according to (1) further including a second lightsource which emits light that enters the light modulation layer from asecond side opposite a first side from which the light from the lightsource enters the light modulation layer and traveling in the lightmodulation layer, wherein the controller controls the scattering statein the divided areas on the basis of distances between the divided areasand the first side and distances between the divided areas and thesecond side.

(6) A display device including:

an image display panel which updates an image in a frame cycle;

a light modulation layer disposed at a back of the image display paneland switched to a scattering state in which incident light is scatteredor a transmission state in which the incident light is transmittedaccording to an electric field applied;

a first light source which emits light that enters the light modulationlayer from a first side thereof and travels in a first direction in thelight modulation layer;

a second light source which emits light that enters the light modulationlayer from a second side opposite the first side and travels in a seconddirection reverse to the first direction in the light modulation layer;

electrodes which are formed according to divided areas of the lightmodulation layer arranged in the first and second directions and whichapply the electric field to the light modulation layer; and

a controller which selects the divided areas in a determined order,which drives the electrodes corresponding to the divided areas on thebasis of distances between the selected divided areas and the first sideand distances between the selected divided areas and the second side,and which controls the scattering state according to the divided areas,during a backlight scanning period corresponding to a frame period.

(7) The display device according to (6), wherein the controller puts thedivided areas into the scattering state in an order in which the imagedisplay panel ends image scanning.

(8) The display device according to (6), wherein the controller:

sets, during the backlight scanning period, assigned drive periodsduring which control is exercised so as to put the divided areas intoscattering state; and

controls a drive current for driving at least one of the first lightsource and the second light source during the assigned drive periods ofthe divided areas on the basis of first amounts of decreases inluminances of the light from the first light source which enters thelight modulation layer from the first side corresponding to distances tothe divided areas and second amounts of decreases in luminances of thelight from the second light source which enters the light modulationlayer from the second side corresponding to distances to the dividedareas.

(9) The display device according to (6), wherein the controllercontrols, during the backlight scanning period, scattering time forwhich the divided areas are put into the scattering state on the basisof first amounts of decreases in luminances of the light from the firstlight source which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas.

(10) The display device according to (6), wherein the controller:

sets assigned drive periods by uniformly distributing the backlightscanning period to the divided areas; and

assigns an idle time of a first divided area whose scattering time forobtaining a required luminance is shorter than the assigned drive periodto a scattering time of a second divided area whose scattering time islonger than the assigned drive period on the basis of first amounts ofdecreases in luminances of the light from the first light source whichenters the light modulation layer from the first side corresponding todistances to the divided areas and second amounts of decreases inluminances of the light from the second light source which enters thelight modulation layer from the second side corresponding to distancesto the divided areas.

(11) The display device according to any of (6) to (10), wherein thecontroller controls the scattering state according to the divided areason the basis of first amounts of decreases in luminances of the lightfrom the first light source which enters the light modulation layer fromthe first side corresponding to distances to the divided areas andsecond amounts of decreases in luminances of the light from the secondlight source which enters the light modulation layer from the secondside corresponding to distances to the divided areas and on the basis oftotal luminance obtained by totalizing luminances of the light from thefirst light source which enters the divided areas and luminances of thelight from the second light source which enters the divided areas.

(12) The display device according to (6), wherein on the basis of firstamounts of decreases in luminances of the light from the first lightsource which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas, the controller:

selects one of the first light source and the second light sourceluminances of incident light from which are higher in the divided areas;and

makes the first light source or the second light source selected on andmakes the first light source or the second light source not selectedoff, for periods for which the divided areas are put into the scatteringstate.

(13) The display device according to (12), wherein the controllercontrols scattering time for which the divided areas are put into thescattering state on the basis of the first amounts of decreases inluminances or the second amounts of decreases in luminancescorresponding to the first light source or the second light sourceselected.

(14) The display device according to (12), wherein the controllercontrols, in periods in which the divided areas are put into thescattering state, a drive current for driving the first light source orthe second light source selected for scattering time for which thedivided areas are put into the scattering state on the basis of thefirst amounts of decreases in luminances or the second amounts ofdecreases in luminances corresponding to the first light source or thesecond light source selected.

(15) The display device according to (12), wherein the controller:

analyzes image signals written to areas of the image display panelcorresponding to the divided areas; and

makes, when a divided area is a target of a luminance increase on thebasis of an analysis result by which an intensity of light emitted fromthe divided area is higher than intensities of light emitted fromsurrounding divided areas, the first light source and the second lightsource on for scattering time for which the divided area is put into thescattering state.

(16) The display device according to (6), wherein the controller:

selects a first divided area and a second divided area disposed betweenthe first divided area and the second side; and

exercises control so that a first scattering time for which the lightfrom the first light source entering the first divided area is scatteredcoincides with a second scattering time for which the light from thesecond light source entering the second divided area is scattered.

(17) The display device according to (6) further including a framememory which stores image signals corresponding to at least one frameperiod inputted in order, wherein the controller:

analyzes image signals corresponding to one frame period stored in theframe memory;

calculates a luminance profile of a backlight; and

generates, on the basis of the luminance profile of the backlight, adrive pattern for driving the first light source, the second lightsource, and the electrodes.

All examples and conditional language provided herein are intended forthe pedagogical purposes of aiding the reader in understanding theinvention and the concepts contributed by the inventor to further theart, and are not to be construed as limitations to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although one or more embodiments of thepresent invention have been described in detail, it should be understoodthat various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

What is claimed is:
 1. A display device comprising: a light modulationlayer switched to a scattering state in which incident light isscattered or a transmission state in which the incident light istransmitted according to an electric field applied; a first light sourcewhich emits light that enters the light modulation layer from a firstside thereof and travels in a first direction in the light modulationlayer; a second light source which emits light that enters the lightmodulation layer from a second side opposite the first side and travelsin a second direction reverse to the first direction in the lightmodulation layer; electrodes which are formed according to divided areasof the light modulation layer arranged in the first and seconddirections and which apply the electric field to the light modulationlayer; and a controller which selects the divided areas in a determinedorder, which drives the electrodes corresponding to the divided areas onthe basis of distances between the selected divided areas and the firstside and distances between the selected divided areas and the secondside, and which controls the scattering state according to the dividedareas, during a backlight scanning period corresponding to a frameperiod.
 2. The display device according to claim 1, wherein thecontroller: sets, during the backlight scanning period, assigned driveperiods during which control is exercised so as to put the divided areasinto scattering state; and controls a drive current for driving at leastone of the first light source and the second light source during theassigned drive periods of the divided areas on the basis of firstamounts of decreases in luminances of the light from the first lightsource which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas.
 3. The display device according to claim1, wherein the controller controls, during the backlight scanningperiod, scattering time for which the divided areas are put into thescattering state on the basis of first amounts of decreases inluminances of the light from the first light source which enters thelight modulation layer from the first side corresponding to distances tothe divided areas and second amounts of decreases in luminances of thelight from the second light source which enters the light modulationlayer from the second side corresponding to distances to the dividedareas.
 4. The display device according to claim 1, wherein thecontroller: sets assigned drive periods by uniformly distributing thebacklight scanning period to the divided areas; and assigns an idle timeof a first divided area whose scattering time for obtaining a requiredluminance is shorter than the assigned drive period to a scattering timeof a second divided area whose scattering time is longer than theassigned drive period on the basis of first amounts of decreases inluminances of the light from the first light source which enters thelight modulation layer from the first side corresponding to distances tothe divided areas and second amounts of decreases in luminances of thelight from the second light source which enters the light modulationlayer from the second side corresponding to distances to the dividedareas.
 5. The display device according to claim 1, wherein thecontroller controls the scattering state according to the divided areason the basis of first amounts of decreases in luminances of the lightfrom the first light source which enters the light modulation layer fromthe first side corresponding to distances to the divided areas andsecond amounts of decreases in luminances of the light from the secondlight source which enters the light modulation layer from the secondside corresponding to distances to the divided areas and on the basis oftotal luminance obtained by totalizing luminances of the light from thefirst light source which enters the divided areas and luminances of thelight from the second light source which enters the divided areas. 6.The display device according to claim 1, wherein on the basis of firstamounts of decreases in luminances of the light from the first lightsource which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas, the controller: selects one of the firstlight source and the second light source luminances of incident lightfrom which are higher in the divided areas; and makes the first lightsource or the second light source selected on and makes the first lightsource or the second light source not selected off, for periods forwhich the divided areas are put into the scattering state.
 7. Thedisplay device according to claim 6, wherein the controller controlsscattering time for which the divided areas are put into the scatteringstate on the basis of the first amounts of decreases in luminances orthe second amounts of decreases in luminances corresponding to the firstlight source or the second light source selected.
 8. The display deviceaccording to claim 6, wherein the controller controls, in periods inwhich the divided areas are put into the scattering state, a drivecurrent for driving the first light source or the second light sourceselected for scattering time for which the divided areas are put intothe scattering state on the basis of the first amounts of decreases inluminances or the second amounts of decreases in luminancescorresponding to the first light source or the second light sourceselected.
 9. The display device according to claim 6, wherein thecontroller makes, when a divided area is a target of a luminanceincrease on the basis of an analysis result by which an intensity oflight emitted from the divided area is higher than intensities of lightemitted from surrounding divided areas, the first light source and thesecond light source on for scattering time for which the divided area isput into the scattering state.
 10. The display device according to claim1, wherein the controller: selects a first divided area and a seconddivided area disposed between the first divided area and the secondside; and exercises control so that a first scattering time for whichthe light from the first light source entering the first divided area isscattered coincides with a second scattering time for which the lightfrom the second light source entering the second divided area isscattered.
 11. A light source device comprising: a light modulationlayer switched to a scattering state in which incident light isscattered or a transmission state in which the incident light istransmitted according to an electric field applied; a first light sourcewhich emits light that enters the light modulation layer from a firstside thereof and travels in a first direction in the light modulationlayer; a second light source which emits light that enters the lightmodulation layer from a second side opposite the first side and travelsin a second direction reverse to the first direction in the lightmodulation layer; electrodes which are formed according to divided areasof the light modulation layer arranged in the first and seconddirections and which apply the electric field to the light modulationlayer; and a controller which selects the divided areas in a determinedorder, which drives the electrodes corresponding to the divided areas onthe basis of distances between the selected divided areas and the firstside and distances between the selected divided areas and the secondside, and which controls the scattering state according to the dividedareas, during a backlight scanning period corresponding to a frameperiod.
 12. The light source device according to claim 11, wherein thecontroller: sets, during the backlight scanning period, assigned driveperiods during which control is exercised so as to put the divided areasinto scattering state; and controls a drive current for driving at leastone of the first light source and the second light source during theassigned drive periods of the divided areas on the basis of firstamounts of decreases in luminances of the light from the first lightsource which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas.
 13. The light source device according toclaim 11, wherein the controller controls, during the backlight scanningperiod, scattering time for which the divided areas are put into thescattering state on the basis of first amounts of decreases inluminances of the light from the first light source which enters thelight modulation layer from the first side corresponding to distances tothe divided areas and second amounts of decreases in luminances of thelight from the second light source which enters the light modulationlayer from the second side corresponding to distances to the dividedareas.
 14. The light source device according to claim 11, wherein thecontroller: sets assigned drive periods by uniformly distributing thebacklight scanning period to the divided areas; and assigns an idle timeof a first divided area whose scattering time for obtaining a requiredluminance is shorter than the assigned drive period to a scattering timeof a second divided area whose scattering time is longer than theassigned drive period on the basis of first amounts of decreases inluminances of the light from the first light source which enters thelight modulation layer from the first side corresponding to distances tothe divided areas and second amounts of decreases in luminances of thelight from the second light source which enters the light modulationlayer from the second side corresponding to distances to the dividedareas.
 15. The light source device according to claim 11, wherein thecontroller controls the scattering state according to the divided areason the basis of first amounts of decreases in luminances of the lightfrom the first light source which enters the light modulation layer fromthe first side corresponding to distances to the divided areas andsecond amounts of decreases in luminances of the light from the secondlight source which enters the light modulation layer from the secondside corresponding to distances to the divided areas and on the basis oftotal luminance obtained by totalizing luminances of the light from thefirst light source which enters the divided areas and luminances of thelight from the second light source which enters the divided areas. 16.The light source device according to claim 11, wherein on the basis offirst amounts of decreases in luminances of the light from the firstlight source which enters the light modulation layer from the first sidecorresponding to distances to the divided areas and second amounts ofdecreases in luminances of the light from the second light source whichenters the light modulation layer from the second side corresponding todistances to the divided areas, the controller: selects one of the firstlight source and the second light source luminances of incident lightfrom which are higher in the divided areas; and makes the first lightsource or the second light source selected on and makes the first lightsource or the second light source not selected off, for periods forwhich the divided areas are put into the scattering state.
 17. The lightsource device according to claim 16, wherein the controller controlsscattering time for which the divided areas are put into the scatteringstate on the basis of the first amounts of decreases in luminances orthe second amounts of decreases in luminances corresponding to the firstlight source or the second light source selected.
 18. The light sourcedevice according to claim 16, wherein the controller controls, inperiods in which the divided areas are put into the scattering state, adrive current for driving the first light source or the second lightsource selected for scattering time for which the divided areas are putinto the scattering state on the basis of the first amounts of decreasesin luminances or the second amounts of decreases in luminancescorresponding to the first light source or the second light sourceselected.
 19. The light source device according to claim 16, wherein thecontroller makes, when a divided area is a target of a luminanceincrease on the basis of an analysis result by which an intensity oflight emitted from the divided area is higher than intensities of lightemitted from surrounding divided areas, the first light source and thesecond light source on for scattering time for which the divided area isput into the scattering state.
 20. The light source device according toclaim 11, wherein the controller: selects a first divided area and asecond divided area disposed between the first divided area and thesecond side; and exercises control so that a first scattering time forwhich the light from the first light source entering the first dividedarea is scattered coincides with a second scattering time for which thelight from the second light source entering the second divided area isscattered.